Constructability was a key component on this bridge design project. The existing three-span non-composite steel girder bridge was replaced with a single-span composite steel girder using Accelerated Bridge Construction (ABC) techniques. Major project challenges included railroad coordination, limited crane access and permitting coordination.
As a toll roadway with daily traffic volumes exceeding 30,000 vehicles, limiting traffic impacts on I-76 during replacement was critical to the project’s success. Impacts to the Norfolk Southern Railroad, which passes below the bridge, also factored into the design.
Benesch used Vissim software to model travel impacts and develop a construction schedule for replacing the bridge during two 59-hour weekend closures – using the first weekend to replace the eastbound structure, and the second weekend for the westbound. Benesch held several coordination meetings with the railroad to determine potential time periods for ceasing or limiting rail operations, and worked with the Pennsylvania Turnpike and PennDOT to identify an effective detour route for roadway traffic.
Several ABC techniques were used to build the replacement bridge, which is supported by full height concrete abutments on a micropile foundation. The new substructure was constructed under the existing structure. The new superstructure consists of several prefabricated deck modules with steel girders and a reinforced concrete deck. During the weekend closures, the existing superstructures were demolished, and the modules were lowered into place. Ultra High Performance Concrete (UHPC) was used to join the modules, and required only 12 hours to fully cure. At the end of each weekend, the roadway was reopened to vehicular traffic before the Monday morning rush hour began.