Project Overview
A tight construction timeline and a unique location necessitated an innovative design approach for a short-span bridge replacement project on West Girard Avenue in Philadelphia, Pa. The bridge is located in a highly active area of the city, adjacent to the Philadelphia Zoo and over a CSX freight railroad carrying more than 20 trains per day. Sandwiched between on- and off-ramps for Interstate 76, the bridge supports four lanes of vehicular traffic and includes two trolley tracks and two pedestrian sidewalks. Given the project’s location and the high volume of traffic flowing through the area, officials with the Pennsylvania Department of Transportation District 6 sought a building material that could be installed with speed and efficiency, while minimizing disruption to the public. PennStress of Roaring Spring, Pa., in partnership with engineer of record Michael Baker International of Harrisburg, Pa., and the rest of the project team successfully designed, manufactured, and installed a variety of precast concrete components for the structure.
Complex Site, Innovative Solution
Given the complexity of the site, which also includes water lines, electrical ducts, and other utilities, a major goal for the project was to replace the bridge’s superstructure during two short construction stages, all while maintaining two lanes of traffic and one sidewalk on West Girard Avenue. The project team chose NEXT D precast concrete beams for the bridge deck, which, in addition to saving critical time over a cast-in-place deck solution, met the limited vertical clearance requirements generated by the bridge’s location over the railroad. Crews installed three 8.5-ft-wide and seven 10-ft-wide NEXT D beams. The different beam widths were needed to match the existing bridge’s out-to-out. Each of the NEXT D beams was designed with a nonstandard height to achieve the vertical clearance needed.
As the project progressed, opportunities to integrate other precast concrete solutions arose. For example, curbs and exterior barriers were integrated into the precast concrete beams to serve as a formwork for the sidewalks.
“This allowed for the barriers to arrive to the project site with the architectural details already in place,” said Audrey Corrado, PE, senior associate and bridge department manager with Michael Baker International. “In turn, construction time was even further reduced, ultimately allowing the bridge to reopen more quickly.”
Precast concrete beam placement took place throughout stages 2 and 4 of the seven-stage project. Initial construction involved the installation of a precast concrete plank beam outside the limits of the out-to-out to support a new water line. Once this was completed, NEXT D beams were set in stage 2, which consisted of removing the existing south half of the bridge and the top courses of the masonry stone abutments and installing precast concrete abutment caps along with four of the NEXT D beams. Ultra-high-performance concrete closure pours were leveraged between the abutment caps and the beams. Stage 4 followed the same approach as stage 2 and was performed on the north half of the existing superstructure with five NEXT D beams. Together, these stages were finished in just two weeks, far besting the six-month timeline that would have been required if alternative materials and construction methods were used.
Replacing a deficient structure in an urban environment is no small task, but thanks to the use of precast concrete, the many stakeholders involved experienced minimal disruptions and the result is a positive outcome for all.
Mason Nichols is a Grand Rapids, Mich.-based writer and editor who has covered the precast concrete industry since 2013. |