Transcript Bridges 8th Grade Science Butler Middle School Lowell, MA Bob, Paul and Ms Adams April 24, 2012

Bridges
8th Grade Science
Butler Middle School
Lowell, MA
Bob, Paul and Ms Adams
April 24, 2012
1
Definition of a Bridge
• A structure spanning and providing
passage over a gap or barrier, such as a
river, road, railway or some other
obstacle.
2
Beam
Basic Types of Bridges
Common on Interstate
Highways
Arch
Very Strong
Suspension
Can be quite long and high
Roadway hangs from cables
Can tolerate some movement
in high wind
Bridge Forces
Compress Tension Bend
Shear
(squeeze) (stretch)
(cutting)
Torsion
(twisting)
What kind of Forces?
Tension, Pulling Apart
Compression, Squeeze
Bending, Tension, Compression
Compression
Tension
Forces that can damage a Bridge
Torsion - Twisting
Bending - Pushes two
ends of an object in
same direction
Shearing Forces can also damage a Bridge
Shear - Pushes in
opposite directions
within the material
3 Spans across Merrimack River, Lowell, MA
Forces in a Beam Bridge
Bending, Compression and Tension
Compression Forces
Tension Forces
Reaction
Load
Reaction
Green St. Bridge over Concord River, Lowell, Ma
Arch Bridge Forces
Compression Forces
Reaction
Load
Reaction
Suspension Bridge
Golden Gate, San Francisco, Ca.
Tension Forces
Reaction
Load
Reaction
Newport, RI
Tyngsborough, Ma. Merrimack River
Bridge Street Bridge is a Truss Bridge
Bridge Street Bridge, Lowell, Ma
Which geometric shape is most noticeable and why?
Triangle vs Rectangle
Rigid
Flexible
(can change its shape)
University Ave Bridge, Lowell Ma
Summer
April 9, 2009
Paper Bridge Challenge
Make a Bridge using 4
sheets of paper and a
little tape