I-91 is a key north-south highway in the western part of New England. In the town of Northampton, Massachusetts, the route was completed in 1965 but despite interim repair, four functionally obsolete, structurally deficient bridges were slated for replacement. Two of the bridges carry traffic over Route 5 and tracks of the B&M Railroad and the other two over Hockanum Road, a short distance to the north. Because maintaining the route is so critical, the two temporary bridges were specified to accommodate heavy commercial and non-commercial traffic during the multi-year project.
Acrow’s modular bridges were purchased by contractor J.F. White Contracting Co. and installed in the median at each location to maintain two lanes of uninterrupted traffic flow while each set of northbound and southbound bridges are replaced in sequence. The detour structure over Route 5 and the railroad tracks consists of five spans with a total length of 500 feet and is supported on eight Acrow towers ranging from 29 feet to 38 feet in height. The second Acrow bridge, over Hockanum Road, is a 140-foot-long clear span. Both bridges are 30 feet wide between curbs and have asphalt overlay deck surfaces. Each structure has a TL-4 guide rail system and live load of two lanes of HL-93.
The longer structure was installed with a full cantilever launch method, and the bridge over Hockanum Road used a crane-assisted launch method. The bridge over Route 5 and the railroad tracks was installed in full coordination with the railroad and the Massachusetts Department of Transportation. The location posed unique complexities. The space between Acrow's structures and the existing bridges was extremely limited, and the roadway and rail track below — as well as utilities — needed to be avoided. Acrow's launch sequence provided a seamless installation between existing bridges. Further, Acrow provided temporary support towers on skewed piers that avoided the obstacles below.
Northbound traffic was shifted to the temporary roadway and bridges in mid-May 2022. When construction on the two permanent northbound structures is complete, southbound traffic will be rerouted over Acrow’s bridges during construction of the permanent southbound structures. It is expected that the temporary structures will be in place for the duration of the project, which is anticipated to be completed in 2025.
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“Project owners and contractors are increasingly selecting detour bridges over other re-routing methods during construction projects,” said Nick Rotondo, Acrow’s Business Development Manager - New England. “In addition to making work sites safer, modular detour bridging helps minimize work zone impact on motorists and local businesses.”
