CUMBERLAND COUNTY, PA – Following the successful demolition and replacement of the eastbound structure, the westbound I-76 structure at Mile Post 238 has followed suit, reopening to the public at 4:00am EST on Monday, September 30—two hours ahead of schedule after a weekend closure.
The bridge replacement, designed by Benesch, utilized Accelerated Bridge Construction (ABC) techniques in order to limit traffic impacts. Benesch worked with the Pennsylvania Turnpike, Pennsylvania Department of Transportation and Norfolk Southern Railway to develop a staging plan that would limit major construction activities to just two weekend roadway closures, using one weekend for the eastbound portion and another for the westbound.
This past weekend’s closure was action packed, involving the complete demolition and replacement of the westbound I-76 structure over the Norfolk Southern Railroad.
The weekend roadway closure began at 7:00pm EST on Friday, September 27. Shortly after, crews got to work dismantling the existing superstructure and substructure.
By early Saturday morning, crews were prepping for the placement of four prefabricated deck modules as Norfolk Southern continued service below—with approximately one train passing through the construction site per hour.
Four prefabricated modules were used to construct the new superstructure, in addition to several approach slabs. Consisting of steel girders and a reinforced concrete deck, the modules were dropped into place, one after the other, on Saturday.
The modules were constructed approximately 100 yards away from the bridge site during the summer and moved into place for the weekend’s construction activities.
Ultra High Performance Concrete
Ultra High Performance Concrete (UHPC) was used for closure pours. Mixing began shortly after the approach slabs were placed, and the UHPC was poured at midnight. UHPC requires a 12-hour cure time to achieve the required 12ksi.
Reopening the Roadway
Roadway paving, drainage and guide rail installation began on Sunday afternoon, after the UHPC was cured. Working through the night, crews were able to reopen to I-76 traffic at 4:00am, two hours before the scheduled end time for the closure.
Supporting the New Superstructure
Prior to the two weekend closures, a new substructure was constructed beneath the existing bridge. Placed between existing bridge spans 1 and 3, the substructure consists of micropiles supporting cast-in-place concrete abutments. Given the tight underclearance and concern for obtaining proper compaction behind the abutments, a flowable fill was used for backfilling.
The substructure was completed during the winter of 2018/2019.
Benesch served as the lead designer on the project and provided construction consultation services for shop drawing reviews and RFIs. J.D. Eckman, Inc., is the contractor.
The remaining work on the project includes final approach roadway paving, existing pier substructure removal and final restoration. The project is expected to be fully complete in November 2019.