Introduction – What is Frith? 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.
Introduction Current Bridge Location Pine River Nature Center Pine River Where is the Bridge?
About Truss Bridges – Truss Intro 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. What Truss Bridges Are
About Truss Bridges – Pony vs Through 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
About Truss Bridges - Deck and Arch 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. Truss Bridge Types
About Truss Bridges – Truss Parts The different parts of a truss bridge are all named. Some of the parts: Top / Upper ChordVertical Member Diagonal Member Bottom / Lower Chord Portal Bracing Sway Bracing V-lacing on vertical member Parts of a Truss Bridge
About Truss Bridges - Connections The pieces of the framework of a truss bridge are held together by connections. Connections can be either riveted or pinned. Pinned connections can be identified by the bolt going through the loops of the members. Riveted Pinned Connections: Riveted / Pinned
About Truss Bridges - Pratt 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
About Truss Bridges – Warren 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. In a Warren configuration, diagonal members angle in alternating directions, forming a “v” shape. Vertical members may separate some of these v shapes. Configuration of Trusses
About Truss Bridges – Complexity 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. Complexity and Beauty
About Truss Bridges – 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
About Truss Bridges – 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
About Truss Bridges – 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! Truss Bridge Reality
Technical Information – Frith Road The Frith Road Bridge Its connections are pinned. The Frith Road Bridge is a Pratt through truss.
Technical Information – 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. Spans and Size Including the approaches, the bridge is 180 feet long. Excluding the approaches, the bridge is about 113 feet long.
Technical Information – Approaches 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. Approaches West Approach (2 Spans) East Approach (1 Span)
Technical Information – Approach Supports and Abutments 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 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.
Technical Information – Main Span Supports 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.
Technical Information – Deck 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. Deck Structure
Technical Information – V- Lacing V-lacing is present on the sway bracing and vertical members. V-Lacing
Technical Information – Portal Bracing The portal bracing on the Frith Road Bridge is referred to as an “A-Frame” design. Portal Bracing 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.
Technical Information – 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. Turnbuckles Newer turnbuckles welded on.
Technical Information – Diagonal Bracing Rods The diagonal bracing between the top chords appears to have been rebuilt or repaired. Diagonal Bracing Rods Redone connection. Part of the original connection.
Technical Information – 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. 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.
Technical Information – Crash Damage 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.
History – The Beginning 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.
History - Significance 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.
History – Local Importance Local Importance 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. Frith Road Bridge is the last through truss bridge on St. Clair County Roads. Frith Road Bridge has a large amount of local significance and rarity.
History – A Rough Survey A Rough Survey Sanilac County is left with one pony truss bridge, scheduled for demolition. Oakland county has no truss bridges! 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. 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: ! X ! !
History – A Rough Survey 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.
Bridge Condition - Paint 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.
Bridge Condition – Rust Damage 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.
Bridge Condition – Connections Connections Connections along the deck have taken a lot of damage from the rust.
Bridge Condition – Broken Rods Broken Rods Some bracing rods under the deck have rusted so bad that they have broken off and bent.
Bridge Condition – Rivet Rust 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!
Bridge Condition – Looking at the Bright Side 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.
Bridge Condition – Looking at the Bright Side Looking at the Bright Side The Frith Road Bridge is in bad condition, but it is still definitely restorable. The bridge has sat un- cared for long enough… it is time to start working to save it!
Restoration - Beyer Road Example Restoration: Beyer Road Bridge This bridge is located just west of Frankenmuth and was restored at its original location. Example Restoration
Restoration - Repairing Joints 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
Restoration - Before and After Example Restoration: Beyer Road Bridge BeforeandAfter Example Restoration
Restoration - 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! Example Restoration
Restoration - Grand Finale 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