I-78 Under Clearance Bridge Project

The Pennsylvania Department of Transportation (PennDOT) sought to replace six bridges over I-78 to increase the minimum vertical clearance and to accommodate future widening. Alfred Benesch & Company and JMT were independently selected by PennDOT to design two separate packages, each consisting of three structures along this corridor located between Harrisburg and Allentown in Berks County, PA. Initially, these bridges were to be constructed using conventional techniques under staged construction maintaining a single lane of traffic in each direction. At the midpoint of the design process, PennDOT asked the teams to merge their efforts and produce a single bid package that incorporated accelerated bridge construction (ABC) techniques under roadway closures to accelerate both the design process and the construction duration of this combined project. In addition, some economy of scale was anticipated considering the similarities of the six structures.

All existing structures were three-span bridges with short end spans comprised of spread box beams and a longer center span over I-78 consisting of adjacent box beams. The existing piers were multicolumn bents supported on spread footings, while the abutments were stub abutments supported on piles. All six of the replacement bridges consisted of single-span prestressed concrete beam bridges that included aesthetic requirements, such as the use of an architectural finish and stain. The abutments were typically tall cantilever abutments supported on spread footings. ABC components utilized on the project included prefabricated bridge elements (footings, stems, pedestals, back walls, deck panels, approach slabs, sleeper slabs, and moment slabs) and the use of ultra high-performance concrete

The use of ABC greatly shortened the on-site construction duration for each of the six structures. Each of the six structures would have taken a full construction season to complete. With the implementation of ABC under roadway closures, the on-site construction time for each of the six bridges was reduced to 30 to 60 calendar days. The project met the owner’s needs of providing standard interstate under clearance and allowing for the future reconstruction of I-78 while maintaining four lanes of traffic on either side as well as leaving behind an aesthetically pleasing group of structures.