Adams Street Viaduct and Rehabilitation of the Adams Street double-leaf, Chicago-Style Trunnion Bascule Bridges
Best Project

Owner: Chicago Dept. of Transportation
General Contractor/Construction Manager: Walsh Construction
Lead Design Firm: Crawford Murphy Tilley (With Collins Engineers)
Structural Engineer: Milhouse Engineering & Construction

The Adams Street Bridge is an iconic bascule bridge servicing nearly 60,000 commuters in downtown Chicago, but at 90 years old, the bridge and the nearby Adams Street Viaduct were in need of major upgrades by the time Milhouse Engineering & Construction began work on them in January 2016.

During the 13-month project, construction manager Walsh Construction demolished the existing viaduct over Union Station and built a new one. The work, which extends over the train station’s 12 platform tracks, spans 282 ft and provides three lanes of traffic and sidewalks.

Bridge work involved rehabilitation of the longitudinal girder, which carries more than 1.1 million lb and itself weighs over 55,000 lb. An entire system had to be created to jack the bridge counterweight—bascule bridges open like teeter-totters with a steel counterweight used as the big kid on one end. The system also had to support the leaf from the live load bearings and finally remove and replace the massive girder. In addition, Milhouse had to work closely with Chicago Union Station and Amtrak in order to proceed with daily operations over live train tracks.

The rehabilitation of the bridge houses restored the structures to a condition similar to when they were built in 1922. This required extensive masonry replacement and a complete renovation to the windows, doors and an ornamental metal roof.

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