Transcript Please Save Frith Presentation

Frith Road
Bridge?
The Frith Road Bridge, crossing the Pine River in St. Clair County, is a historic
metal truss bridge that does not meet the county's requirements for weight
and traffic capacity. The St. Clair County Road Commission wants to build a
replacement bridge. They are willing to give the historic bridge to Pine River
Nature Center.
Where is the
Bridge?
Pine River Nature Center
Pine River
Current Bridge Location
What Truss
Bridges Are
Truss bridges are bridges whose main structure is a triagular framework.
The Original Blue Water
Bridge is a special type of
truss bridge and is known as
a cantilever bridge.
Truss Bridge
Types
If the trusses run beside the deck, with no cross bracing
above the deck, it is called a pony truss bridge.
If cross-bracing is present above the deck of the bridge, then
the bridge is referred to as a “through truss.”
Truss Bridge
Types
If trusses run under the deck, then
the bridge is a deck truss bridge.
This bridge is not a truss bridge,
although it is referred to as a
trussed arch, since the arch is built
of a triangle framework.
Parts of a
Truss Bridge
The different parts of a truss bridge are all named. Some of the parts:
Top / Upper Chord
Vertical Member
Diagonal Member
Bottom / Lower Chord
Portal Bracing
Sway Bracing
V-lacing on vertical
member
Connections:
Riveted / Pinned
The pieces of the framework of a truss bridge are held together by
connections. Connections can be either riveted or pinned.
Riveted
Pinned
Riveted
Pinned
Riveted
Pinned
Pinned connections can be identified by the bolt going through the loops of
the members.
Configuration
of Trusses
There are several ways of configuring the diagonal members of truss
bridges. The most two common configurations are Pratt and Warren.
In a Pratt configuration, diagonal members angle towards the center and
bottom of the bridge.
Sometimes extra and often
smaller diagonal members
may be present that do not
follow this rule.
Configuration
of Trusses
In a Warren configuration, diagonal members angle in
alternating directions, forming a “v” shape. Vertical members
may separate some of these v shapes.
Although not always, Pratt configurations tend to be on older
turn of the century truss bridges, and Warren configurations
tend to be on the newer 1920s-30s truss bridges.
Complexity
and Beauty
Truss bridges are a very complex type of bridge. Intricate geometry and
engineering works together to hold these structures up. There are many
more configurations, shapes of truss bridges, and there can be
combinations of those.
Truss bridges are a work of intricate art as well. Whether it is a huge
landmark bridge, or a small bridge tucked away in the country, each one
is unique in its own way. These bridges were built in a time when a lot
more attention was paid to detail and aesthetic appearance.
Truss Bridge
Reality
Despite their complexity, truss bridges are a thing of the past. The truss
bridge era began roughly in the 1880s and ended roughly in the 1930s.
Modern bridge building has reached an unprecedented simplicity. Truss
bridges are usually replaced with what amounts to a simple slab of concrete
held together by reinforcing rods. These modern bridges are built to a
standard plan and they all look the same. Some modern bridges are so plain
that you might not even notice if you are crossing one. Bridges built today
are no longer eye-catching landmarks.
Truss Bridge
Reality
The Church Road Bridge located south of M-46 near Carsonville in Sanilac
County was replaced in the Summer of 2004. The pictures below contrast the
through truss bridge to the replacement concrete span.
Truss Bridge
Reality
Although a few have been preserved, the majority of
truss bridges have been demolished, are going to be
demolished, or are simply abandoned to rot away.
This is why we need to save the Frith Road Bridge!
The Frith
Road Bridge
The Frith Road Bridge
is a Pratt through
truss.
Its connections are pinned .
Spans and
Size
The Frith Road Bridge
includes wooden
approach spans at
each end and the
main steel truss span.
The deck of the
bridge is 16 feet
wide.
From the bottom of
the deck to the top of
the sway bracing, the
bridge is 20 feet.
Including the approaches, the bridge is 180 feet long.
Excluding the approaches, the bridge is about 113 feet long.
Approaches
West
Approach
(2 Spans)
East
Approach
(1 Span)
Simple beam spans
provide an approach
to the bridge.
There are two
approach spans at the
west end, and one
approach span at the
east end.
They are constructed
of wood stringers and
supported by
concrete.
Each span is 22 feet
long.
Approach Supports
and Abutments
The abutments for the bridge are of
concrete, and are similar in
appearance to the approach supports.
Compared to other historic truss
bridges, these abutments are simple
in design and very small.
The approach spans are held up
by the abutments, and the main
span supports. The west approach
also has a concrete pier.
The west approach concrete
support appears to have been
repaired at some time
Main Span
Supports
The main truss
span is supported
by steel caissons,
which are filled
with concrete on
the inside.
Some of these
caissons have
slowly been
beginning to tip
over, which will
begin to put the
bridge at risk if
not dealt with.
Deck
Structure
The deck is wooden with an asphalt layer on top. This is not the original
deck.
Support under the bridge comes from both steel i-beams as well as wooden
beams.
The only place where paint appears to be is on the steel i-beams. This paint
is a rusty red in color.
V-Lacing
V-lacing is present on the sway bracing and vertical members.
Portal Bracing
The portal bracing on the Frith Road Bridge is referred to as an “A-Frame”
design.
Portals and guardrails (if original) are widely varied, and were a portion of
the bridge where the builders could use their imagination.
The Frith Road Bridge’s portal bracing would have been considered plain
and simple when it was built. Nevertheless, it is still a very attractive part of
the bridge.
Turnbuckles
Turnbuckles are
present on the
diagonal members
which were
designed to adjust
tension.
One set of the
turnbuckles appears
to have been
replaced long ago.
Newer
turnbuckles
welded on.
Diagonal
Bracing Rods
The diagonal bracing
between the top chords
appears to have been
rebuilt or repaired.
Part of the
original
connection.
Redone
connection.
Guardrails
The original guardrails have
been replaced with modern
guardrails. This was supposedly
done in the 1970s.
A historical photograph of the
bridge indicates that the bridge
originally had simple metal
pipes for guardrails.
These guardrails are mounted directly to the v-laced vertical members
of the bridge, rather than to the deck or i-beams below. The weight of
the guardrails, which essentially are hanging on the bridge, are slowly
enlarging the holes where the bolts go through the vertical member.
Crash Damage
Frith Road Bridge was closed January 9, 2004 after a car hit the
guardrails and damaged one of the vertical members.
Because the guardrails are attached directly to the vertical members,
the guardrail transferred the impact pressure directly to the bridge.
The Beginning
Construction of the Frith Road
Bridge was undertaken in
1914 supposedly by the
township, and remained under
township jurisdiction until
1934.
Historic maps indicate that the
current truss bridge was not
the first crossing at the
location.
A school was located in the
area near the bridge.
On March 13, 1934, Frith
Road, including the bridge,
was transferred to the St.
Clair County Road
Commission.
Statewide
Significance
The Frith Road Bridge was one of the last pin
connected Pratt through truss bridges built in
Michigan.
Its length is considered long due to the approach
spans. It is 180 feet in all.
It is a good example of the traditional Pratt
through truss bridge design.
Local
Importance
Frith Road Bridge has a large amount of local significance and rarity.
Frith Road Bridge is the last through truss bridge on St.
Clair County Roads.
The demolition of the Church Road Bridge near Carsonville in the summer
of 2004 made this bridge the last through truss bridge in the eastern part
of the thumb.
If current plans to relocate or
demolish the Indian Trail and
Speaker Road pony truss bridges
succeed, Frith Road Bridge will be
the last highway truss bridge of any
kind in St. Clair County.
A Rough
Survey
In my efforts to locate and photograph area truss bridges, I learned
how scarce truss bridges are by writing the road commissions and
requesting locations of any truss bridges:
!
Sanilac County is left with
one pony truss bridge,
scheduled for demolition.
!
Macomb County has three
pony truss bridges, all
abandoned and in very
poor condition.
!
Tuscola County has one pony
truss, scheduled for
demolition in 2005.
X
Oakland county has no truss
bridges!
A Rough
Survey
Saginaw County is the closest happy story, with two restored through
truss bridges, and several other abandoned truss bridges. The closest
restored bridge is 70 miles away from the Pine River Nature Center
and is just outside Frankenmuth.
Paint
The Frith Road Bridge Needs Help!
The Frith Road Bridge is a steel bridge, and should have a layer of
paint to protect it. The Frith Road Bridge has rusted so much that
there is no paint visible on any part of the bridge, with the
exception of possible paint on the i-beams below the deck.
Rust Damage
Rust: A Truss Bridge Killer
The severe rust which has developed has caused considerable
damage to many areas of the bridge under or beside the deck.
Connections
Connections along the deck have taken a lot of damage from the
rust.
Broken Rods
Some bracing rods under the deck have rusted so bad that they
have broken off and bent.
Rivet Rust
Some of the rivets inside the top chord near the deck have rusted
so bad, that they look like some sort of strange fungal growth on
the bridge!
Looking at the
Bright Side
At the opposite end, the situation is much brighter, and not just
because of the sunlight – there is much less rust damage up here.
Looking at the
Bright Side
The Frith Road Bridge is in bad condition, but it is
still definitely restorable. The bridge has sat uncared for long enough… it is time to start working
to save it!
Example
Restoration
Example Restoration: Beyer Road Bridge
This bridge is located just west of Frankenmuth and was restored at
its original location.
Example
Restoration
Example Restoration: Beyer Road Bridge
Repairs made to the approach span (left) show how a rusted joint, as
seen on the main span (right) can be repaired.
Example
Restoration
Example Restoration: Beyer Road Bridge
Before
and
After
Example
Restoration
Restoring a historic truss bridge really does give
the bridge a new life:
Hopefully, this new life can be given to the
Frith Road Bridge!
A New Life
Restoring a historic truss bridge really does give
the bridge a new life:
Hopefully, this new life can be given to the
Frith Road Bridge!