Transcript NOT
Slide 1
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 2
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 3
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 4
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 5
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 6
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 7
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 8
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 9
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 10
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 11
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 12
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 13
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 14
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 15
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 16
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 17
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 18
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 19
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 20
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 21
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 22
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 23
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 24
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 25
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 26
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 27
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 28
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 29
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 30
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 31
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 32
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 33
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 34
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 35
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 36
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 37
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 38
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 39
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 40
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 41
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 42
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 43
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 44
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 45
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 46
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 47
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 48
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 49
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 50
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 51
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 2
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 3
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 4
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 5
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 6
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 7
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 8
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 9
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 10
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 11
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 12
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 13
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 14
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 15
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 16
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 17
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 18
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 19
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 20
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 21
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 22
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 23
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 24
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 25
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 26
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 27
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 28
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 29
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 30
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 31
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 32
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 33
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 34
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 35
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 36
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 37
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 38
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 39
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 40
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 41
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 42
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 43
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 44
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 45
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 46
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 47
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 48
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 49
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 50
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!
Slide 51
The 13th Annual Strongsville Truss
Structure Competition
indianalandmarks.org
The Basics
• You will work in groups of 13 students to build
TWO balsa wood bridges.
– If you chose to work in a group you must work with someone taking regular
physics.
– you will have the option after you build and test the first bridge to leave your
group. You will not be permitted to change groups, but you can leave your
group and go solo.
• You will RESEARCH the concepts of stress and
strain as well as different bridge/truss styles. This
research will help you to design and build a
(hopefully) strong/efficient structure that is made of
an inherently weak material.
• Your teacher will eventually break your bridges
Why 2 bridges?
• You will learn SO MUCH about the bridges
(and stress and strain) when you see them
break.
• We want you to actually learn from this
experience and improve upon what you
have already done (with bridge 1)
But, what if I’m awesome…and
can’t improve?
• First of all…you can improve!
• But, we have a plan for that.
– If your first bridge is truly awesome you can
opt out of the second bridge…
• Check the rules sheet.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 1 – Due February 21
– Must submit diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 12.5 pounds
– Will be graded based on 3 things:
(1) met specifications and diagrams
(2) held minimum weight
(3) efficiency ratio*
» See rules sheet for details
Bridge 1 - rubric
GRADING
Bridge 1
Tier 1
Specifications
met?
Yes = 15 / 15
Tier 2
Tier 3
Tier 4
Tier 5
Yes = 15 / 15
No = maximum points
available 10/15 (but
No and NOT testable.
Non-Droppable Zero!
No* = maximum points
available 10/15 (but
could be lower – depending
on violations)
*still “testable”
could be lower – depending
on violations)
*still “testable”
Minimum weight
held
Yes = 7.5 / 7.5
Yes = 7.5 / 7.5
NO = 0 / 7.5
NO = 0 / 7.5
NOT testable.
Non-Droppable Zero!
Efficiency
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
See Ratio Scale for
your points.
Maximum points
available are 7.5/7.5
NOT testable.
Non-Droppable Zero!
Maximum score
available
CAN earn up to 30/ 30
points
CAN earn up to
25/30 points
CAN earn up to
22.5/30 points
CAN earn up to
17.5/30 points
Non-Droppable Zero!
What’s this “ratio” thing about?
Your bridges will be judged on a ratio of how
strong they are to how heavy they are.
It would be very easy to build a very heavy
bridge that can hold a lot of weight….that’s
not the goal.
You want a high ratio of weight held to
weight of bridge.
You want to build an efficient bridge…light
but strong!
What’s this “ratio” thing about?
Efficiency Ratio = weight held (Lbs) x 456 (grams/Lb)
Mass of structure (grams)
We have to convert to a common unit.
The Basics
• Yes…we said TWO (2) Bridges.
• Bridge 2 – Due April 9, 2013
• Must submit updated diagrams (see rules sheet)
– Must meet all required dimensions
– Must hold a minimum of 22.5 pounds
– Will be graded based on 5 things:
(1) met specifications
(2) modifications to original design
(3) minimum weight held
(4) efficiency ratio
» See rules sheet for details
HEADS UP…this is VERY EARLY in 4th quarter!
Bridge 2 - Rubric
The Dimensions
• You have some room to design as you
like, but you are limited in the dimensions
a bit.
Top must be between 20.00 and 60.00 cm
Minimum
Total height
= 15.00 cm
Max below
roadway =
base = span = exactly 60.00 cm
7.00 cm
In addition….your bridge MUST BE 10.00-cm wide (outside to outside) at all points
and can be no more than 80.00grams.
More details…
• To test/break your bridge we will insert a
wood block into the side of the bridge.
You MUST leave an opening in the side(s)
of your bridge so that the block fits!
Width of block
Length of testing block = 9.8-cm
(careful this is narrower than the bridge)
Height of block
Height of testing block = 3.1-cm
Width of testing block= 6.3-cm
Testing
Block
Length of block (9.8-cm)
– this goes ACROSS
the width (10.00cm) of
your bridge
Even more details…
• To test your bridge you will place it
between two lab tables as shown below.
Your
“roadway”
must be
“level” with
the table.
No higher
than 1.0inch
1 inch
span = 60.00
7/8cm
inch
1 1/8
inches
Remember that you
also have the option to
build underneath the
roadway. Max = 7.0-cm
Two metersticks will
be stacked
up and
clamped to
the table to
give your
bridge
something
to push
against
(anchor it)
One more thing…
What do you build this out of?
• ¼ inch thick BALSA wood
• Or thinner!
• You can buy the planks or the sticks…it doesn’t
matter to me (but it will matter in $$$)
• Make sure that you buy BALSA wood, not BASS
wood.
• Any one-part glue.
• Be careful with the glue…some glues are really
heavy.
What?
Here…let us show you….
• PLEASE NOTE…
The bridges in this show were tested using the
honors testing block. Regular physics students
need to be aware that their bridges will be tested
with a smaller rectangular block.
However, the regular testing block will also be
placed on the road way in the center of the span.
When constructing your bridge, pay attention to
where the block will be placed.
The Testing Set Up
Honors testing
block!
Length = 60 cm
You can build beneath the road/deck of the bridge, but make sure that it fits!
The Testing Set Up
Again, this is
the honors
testing block!
Pay attention to
the dimensions
of the testing
block – if it
doesn’t fit IN the
bridge, the
bridge cannot
be tested!
Length = 60 cm
Length = 60 cm
The other side
of this bridge
was open;
allowing the
block to slide in
from just one
side.
Good Idea or
Bad Idea?
Length = 60 cm
This bridge was
made using Ibeams.
You can NOT
use I-beams!
Length = 60 cm
7-cm under “roadway”
Remember…
Your design must allow for the bus to travel down the length of the
bridge as well as the testing block to fit across the center of the bridge.
This
bridge
DOES
allow for
passage
down the
bridge.
If the bridge does not have a clear
passage way, points will be deducted.
These designs do NOT allow for travel down the
bridge.
This bridge DOES NOT allow for
passage down the bridge. They
blocked off the ends!
NOT
You are
permitted
to place the testing block on
TOP of the structure.
This is NOT a LEGAL test
This resulted in a
non-droppable zero!
The testing block
must go on the
“roadway” which
can be no higher
than 1-inch above
the table top.
Don’t get too attached….
Legal Truss Systems
The following are common truss systems. You
may use variations of the following:
• King Truss
Hint…LOOK online and around the
• Warren Truss
real world at some bridges. Don’t
try and come up with something
• Pratt Truss
new…adapt what’s already out
there to fit the needs for this
• Lattice Truss
project.
• Whipple Truss
You cannot just build a box (“box truss”) – that is
NOT the intension of the project and will earn
you a non-droppable zero!
Legal Joints
Single overlapping joint
1in
Legal Joints
Double overlapping joint
1in
You are NOT permitted to “stack” joints.
You may have a
double overlap with
UP TO 4 pieces.
You may NOT
stack/overlap more
than 4 pieces!
This IS legal
as long as
the overlap is
within the ½
inch
allowance!
This IS NOT
legal!
You may not
“stack” the
beams!
Legal Joints
Butt joint
This is when two pieces of wood
are “butted” up against each other
(end to end)
1in
Legal Joints
Gusset Plate
no bigger than 1-in2
Gusset Plate
This is a SMALL square of wood
that protects the joint underneath.
This can be placed over any of the
(legal) joints mentioned. NOTE
THE DIMENSIONS!
You are NOT permitted to “stack” joints.
This is a legal gusset
joint
This is two butt-joints protected
by a gusset plate.
This is NOT legal!
Good joints!
Pieces are notched so they fit
snugly. This is strong as long as
you don’t cut through too much of
the board.
Gusset plate
NO I-Beams
I-beams are
NOT
permitted!
NO H-Beams
H-beams are
NOT
permitted
and they are dumb.
NO Lamination!
• Lamination is the stacking of pieces of
balsa wood as shown below. THIS IS
NOT PERMITTED!
1/4” or less
1/4” or less
You must be very careful with your joints.
If you have too much area overlapping it
will be considered lamination.
All members must be structural in nature. You can
NOT add members just to meet the requirements!
Something like this will result in a disqualification!
Come on…really?
You ARE permitted to measure the
dimensions of the desk edge and build your
structure so that it fits the gap.
Note – the meterstick will be placed 1.0-cm
away from the edge of the table.
Building Tips
• Choose your wood wisely!
– Make sure that you purchase BALSA wood!
– Choose wood that is straight and dry!
– Balsa is inherently weak, but try to choose pieces with few flaws
• Cut your pieces with a sharp X-acto® knife OR use a
miter box and small craft saw.
• Give yourself PLENTY of time to build!
• Create actual size “building plans” that will allow you to
easily put your members together. Put a piece of wax
paper over the plans then place objects directly over top
to ensure that all pieces are cut to the appropriate size
and glued in the correct manner.
•
The wax paper keeps the glue from sticking to your actual plans.
Important Information
Bridge 1
Due on February 21, 2013
You must have your plans (printed) and bridge in class and ready to
impound.
NO LATE BRIDGES WILL BE ACCEPTED!
Bridge 2
Due on April 9, 2013
You must have your adapted plans and bridge in class and ready to
impound and test
Testing will begin in class on Monday!
NO LATE BRIDGES WILL BE ACCEPTED!
Internet Resources
http://www.brantacan.co.uk/starterpages.htm
This site will help you design your bridge. It also has links to sites that will
“calculate” how your bridge will perform.
http://bridgecontest.usma.edu/
This site has a link to download the West Point bridge design software.
There is a LOT of information on the web for this
stuff…remember this is a RESEARCH PROJECT
so
do some
RESEARCH!
Good Luck!