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Frith Road Bridge

Fitzgerald Road Bridge

Frith Road Bridge

Primary Photographer(s): Nathan Holth and Luke Gordon

Bridge Documented: June 6, 2003 - Fall 2005

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Key Facts

Facility Carried / Feature Intersected
Frith Road Over Pine River
Rural: St. Clair County, Michigan: United States
Structure Type
Metal 7 Panel Pin-Connected Pratt Through Truss, Fixed and Approach Spans: Wood Stringer (Multi-Beam), Fixed
Construction Date and Builder / Engineer
By Builder/Contractor: Unknown

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
112 Feet (34.1 Meters)
Structure Length
179 Feet (54.6 Meters)
Roadway Width
16 Feet (4.88 Meters)
1 Main Span(s) and 3 Approach Span(s)
NBI Number

Historic Significance Rating (HSR)
View Information About HSR Ratings

Bridge Documentation

This bridge is in storage!

Bridge Status: This bridge has been dismantled and is in storage awaiting restoration and reuse in a new location!

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

Frith Road in the area of this bridge long ago went by the name Fitzgerald Road. Few may be aware of this today, but it seems appropriate to note this since the bridge would originally have been known as the Fitzgerald Road Bridge.

This bridge is a seven panel pin-connected Pratt through truss with trusses that are 20 feet high. The Historic Bridge Inventory reported a 1914 construction date, but this date has been disputed and so it is not certain this is when the bridge was built. The bridge does appear to be an early 20th Century bridge, and if the 1914 date is incorrect it would likely be older than 1914, perhaps ca. 1905. It was constructed at the end of the pin-connected truss era, when more rigid riveted connections were gaining popularity. At this time, the pin-connected truss bridge was a tried-and-true method of bridge construction, and standardized parts that had been in use for many years were used to build this bridge. The truss bridge sat on riveted steel caissons filled with concrete, a type of support common in the Midwest during this period in history. The bridge had two wooden approach spans at the western end, and a single wooden approach span at the east end. The main truss span retains good historic integrity. Minor alterations include one diagonal member that had a replacement turnbuckle spliced in at some date long ago. The lateral bracing rods above the road also were removed from their original attachments to the top chord and simply welded to angle, which in turn was welded to the top chord. Some lateral bracing under the deck had broken and fallen away. Floor beams appeared to be original.

Damage and Bridge Closure

In mid-January 2004, the bridge closed to traffic because a car hit a part of the bridge. A field visit quickly revealed that a car had hit and scraped against the modern  guardrail in the center of the north side of the bridge. The modern guardrail had bent out. A vertical member was also slightly bent outward, with its v-lacing buckled as well. This damage to the bridge could have been prevented had the modern, non-original Armco guardrail on the bridge been mounted into the deck of the bridge rather than bolted onto the vertical member. Having been bolted onto the vertical member, the guardrail did little to protect the historic bridge from damage, since it merely transferred the impact damage into the vertical member, which was never designed to take this type of impact stress. This is a lesson to owners of historic bridges. Merely installing a modern guardrail does not provide sufficient protection: the guardrail must be installed correctly. Also, in the interest of historic integrity good practice dictates that if the original railing remains, it should be left in place behind the added modern railing. At some unknown date, the original gas pipe style railings on this bridge were removed. These railings can be seen in a historical photograph of the bridge.

A Future For Frith

This bridge was replaced in 2004, however the truss bridge has been match-marked, carefully disassembled, and placed into storage for future restoration and reuse in a new location. The bridge is feasible to restore for pedestrian use. However, the bridge will require a fair amount of work to restore, most notably due to substantial section loss at the connection points. Despite this, the bridge is still worth restoring, and the cost of the work may still be competitive with costs for a modern pedestrian bridge.

The bridge was originally scheduled to move to the Pine River Nature Center which would have kept it in St. Clair County, however the organization later backed out of the idea. The bridge was then slated to move to the Historic Bridge Park in Calhoun County, Michigan, but this park later decided to stop spending money adding bridges to the unique park. The bridge today would be made available to an interested third party that would commit to restore and preserve this historic bridge. The bridge could also potentially end up as part of a project in Calhoun County to build a trail connecting to the Historic Bridge Park. This trail, like the park, would feature several historic bridges like the Frith Road Bridge on it.

Why bother saving the Frith Road Bridge? What makes a through truss bridge special? The methods and techniques used to build this bridge are no longer used, and have not been used for many decades. The configuration of the steel members of the bridge bears much resemblance to wooden covered bridges. These are the kinds of bridges you see in movies, where a romantic couple walk slowly across the bridge, enjoying the view and one-another's company. The bridge is of considerable length, and is therefore a more significant monument to early 20th century bridge building then shorter examples. The skeletal nature of through truss bridges makes them excellent tools to teach and learn about how compression and tension in the members of a bridge makes a bridge "work."

Building the Frith Road Bridge, back in 1914, was probably a much more complex project for the contractors in 1914, than it was be for today's contractors to build its replacement. Modern motorized machinery was still in an early stage. State standard plans for bridges on roadways were only beginning to develop. Preserving the Frith Road Bridge would be a great way to honor the people who worked hard to keep our country and its people moving so many years ago, so we could progress to where we are in our country today. Metal truss bridges, like the Frith Road Bridge, are a type of bridge that are no longer built on roads today. The few bridges of this type that remain on roadways are often closed to traffic and/or are being demolished at an extremely fast rate. The eastern thumb area is particularly devoid of truss bridges, especially through truss bridges. With the summer 2004 demolition of the Church Road Bridge in Sanilac County, and the collapse of the abandoned Ford Road Bridge in St. Clair County several years ago, the Frith Road Bridge was the last through truss bridge in the eastern thumb area.


This bridge was among the first bridges photographed for HistoricBridges.org, and its photo-documentation dates back to a time when HistoricBridges.org's members spent a lot of time photographing a smaller number of bridges in a more localized region. As such, this bridge has an unusually large collection of photographs for its type. Enjoy the comprehensive photo galleries for this bridge which present this beautiful bridge through the diverse seasons Michigan offers. Also available is a photo gallery showing the bridge being lifted off its abutments and dismantled for storage.

While the Frith Road Bridge may have a future elsewhere, Frith Road itself will never be the same. The ugly two lane replacement bridge that replaced the one-lane historic bridge is an eyesore for the surrounding residents, many of whom would have rather seen the historic bridge rehabilitated for continued light vehicular use. The replacement bridge also eliminated the distinctive kink in the road, which was a remnant of decades long ago when builders would align the bridge to cross the river in the shortest distance possible... an arrangement that often left the bridge's ends misaligned with the actual road's alignment, which necessitated the distinctive kink. Today, the kink is gone, as is the one-lane crossing, enabling cars to travel Frith Road at far higher speeds than before... perhaps speeds that would have been better left on nearby I-94. The below photos show the before and after of Frith Road.

Information and Findings From Michigan Historic Bridge Inventory

Narrative Description

The Firth Road Bridge over the Pine River is located in a rural area southwest of Port Huron. The main span of the bridge is a seven-panel, pin-connected Pratt through truss. A single stringer span provides an approach to the east; to the west are two wood-and-concrete spans. The truss contains the following members: upper chord: back-to-back channels with cover plate and battens; lower chord: two looped bars; end verticals: pair of square-section rods; other verticals: back-to-back channels with V-lacing; diagonals: two looped bars; counter: two looped square-section rods; bottom and top laterals: round rods; portal bracing: paired angles in A-form; sway bracing: two pairs of angles with V-lacing; floor beams: I-beam bolted to angle riveted to plate below vertical; railing: modern metal guardrail.

The original deck and stringers have been replaced by a laminated timber slab. Wood curbs edge the roadway on the approach spans. There are roller bearings at the east end of the truss.

The Michigan Department of Transportation database gives a construction date of 1914. While the floor system has been replaced, and the metal on the truss has rusted, the structure's integrity is relatively good.

This bridge is tagged with the following special condition(s): Available


Photo Galleries and Videos: Frith Road Bridge

View Photo Gallery
Structure Overview
Original / Full Size Photos
A collection of overview photos that show the bridge as a whole and general areas of the bridge. This gallery offers photos in the highest available resolution and file size in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
Structure Details
Original / Full Size Photos
A collection of detail photos that document the parts, construction, and condition of the bridge. This gallery offers photos in the highest available resolution and file size in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
Structure Overview
Mobile Optimized Photos
A collection of overview photos that show the bridge as a whole and general areas of the bridge. This gallery features data-friendly, fast-loading photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
Structure Details
Mobile Optimized Photos
A collection of detail photos that document the parts, construction, and condition of the bridge. This gallery features data-friendly, fast-loading photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
Bridge Dismantling and Replacement
A collection of overview and detail photos documenting the bridge being removed and dismantled for future reuse. Some photos comparing the replacement bridge to the historic bridge are included in this gallery. This photo gallery contains a combination of Original Size photos and Mobile Optimized photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer


Maps and Links: Frith Road Bridge

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