Please Save Frith

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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 Chord Vertical Member

Diagonal MemberBottom / 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 RivetedRiveted

Pinned Pinned 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)

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:

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X

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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 BridgeThis bridge is located just west of Frankenmuth and was restored at

its original location.

Example Restoration

Restoration - Repairing Joints

Example Restoration: Beyer Road BridgeRepairs 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

Before

and After

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 theFrith 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 theFrith Road Bridge!

A New Life

Restoration - Please Save Frith