Bridgeport Bridge

"State Street Bridge"

Bridge Documented: Summer 2007

Technical and Historical Overview

This is a breathtaking two span Pratt through truss bridge, and one of the most significant examples of the Joliet Bridge and Iron Company's work in Michigan. It retains plaques at both ends of the bridge, and also original channel guardrails. Also, due to the fact that it is two-span, it is very rare for Michigan which has an unusually small number of surviving multi-span truss bridges. It is also simply a beautiful bridge, more beautiful than any modern bridge could hope to be with its lightweight yet intricate truss and beam geometry. It is located in a scenic area with a companion historic railroad truss bridge nearby. It is one of the very few places in the entire state of Michigan where more than two or more truss bridges can be seen together. An interesting fun fact is that two different companies fabricated the channels composing the built-up end posts: some channels have Cambria markings, while others have Carnegie markings. It is common to have multiple fabricators for the different types of beams on truss bridges, but it is less common to find multiple fabricators for identical parts/beams.

Prior to restoration, the traditionally composed truss was configured as follows: Connections: pinned with recessed nuts. Top chord and end post: back-to-back channels with v-lacing and cover plate. Bottom chord: up-set eyebars. Vertical members: back-to-back channels with v-lacing on each side. Hip vertical member: loop-forged eyebars. Diagonal members: up-set eyebars. Sway bracing: paired angles with v-lacing between and no knee bracing. Portal bracing: single row of large-size lattice composed of riveted angles, and a knee brace formed from a single angle. Deck: metal deck stringers wooden deck and asphalt wearing surface. Railing: two rows of channel. Floor beams: rolled American Standard i-beams. Lateral bracing: threaded rod with nuts. Identified metal fabricators: Cambria and Carnegie. There also was a partial mark observed on a deck stringer that appeared to be Jones and Laughlin.

2010 Restoration: A Future For The State Street Bridge

The State Street Bridge, one of Michigan's few remaining multi-span metal truss bridges, is being restored for pedestrian use in its original location, representing a major step forward for historic bridge preservation in Michigan. In January 2010, the restoration project for this historic bridge began. The bridge spans have been moved to a temporary restoration work site where they will be restored for placement back over the bridge.

Prior to restoration, there was still some lingering paint on this bridge, although rust had taken a toll on the integrity of some of the bridge including sway bracing at the connection points. One unusual area of heavy deterioration was the top chord cover plate which had significant section loss. However the main need for a restoration project was the substructure of the bridge. The south/west end of this bridge sat on a concrete pier that was rotating, essentially slowly tipping over. For years the south/west truss span had a twisted appearance since the truss had rotated along with the pier. In the final years and even months leading up to restoration, pier rotation had accelerated, and the bridge had become at risk for collapse.

Despite the problems with the bridge, this bridge was still in a restorable condition, and thanks to a number of people committed to ensuring this bridge has a future, a comprehensive restoration project was secured for the historic truss superstructure which will result in this bridge being reopened in its original location for non-motorized traffic. The restoration will replace the deficient and failed substructure, and will execute an in-kind restoration on the truss. In-kind restoration is the preferred type of preservation that ensures that as much original material on the bridge as possible will be preserved, and anything that must be replaced will be exactly replicated and the design and function of the truss must not be altered. Rivets will be replaced with rivets, v-laced beams will be replaced with v-laced beams and not wide-flange beams, etc. There will be no ugly retrofits or welded plates covering the bridge.

The existing approach spans of the bridge will be reused. The substructure for the main spans will be completely reconstructed due to their failed and/or deficient condition. Note that the substructure is not part of the bridge's historic significance. The new substructure will also raise the truss bridge spans up by one foot which will provide the bridge greater protection from flood damage. The bridge will be painted black. The original channel railings are supposed to be placed back on the bridge for the sake of historic integrity, with modern railings being place on the deck in front of those for the sake of safety and code requirements.

Those involved with the restoration of this bridge hope that not only will the bridge improve the quality of life in Bridgeport, but that it will become an example project that will inspire high quality historic bridge preservation elsewhere. HistoricBridges.org thanks Bridgeport Township for initiating this preservation project. Spicer Group is the engineer for the project, and Davis Construction is the contractor. Vern Mesler was retained by Spicer Group to assist in developing the in-kind restoration procedures.

Why Restore The State Street Bridge?

HistoricBridges.org first proposed a preservation solution for this bridge back in 2005. Below is the outline of that proposal, which is in fact exactly what was decided for this bridge.

There are many reasons that this bridge should be restored for pedestrian traffic. The restoration of this bridge would ensure that such a rare and beautiful historic bridge remains around for future generations to enjoy. Also, restoring this bridge would provide people who live in town easy access to the park on the other side of this bridge. The way that this town is set up, with this bridge closed, people who live on the north side of town have to travel several miles to get to the park safely. It is no surprise that many locals use the nearby active railroad  bridge, which is not fenced off, to walk to the park in a matter of minutes. Restoring this bridge would help encourage people to not cross using the railroad bridge, which could be dangerous, especially for children, who HistoricBridges.org observed using the bridge during field visits.

Click Here To See the 2005 HistoricBridges.org Proposal Map Showing The Problem And The Solution