Completed in just 15 days, the widening of a bridge on westbound Interstate 376 (I-376) in Pittsburgh, Pa., was accomplished via a winning combination of ultra-high-performance concrete (UHPC), multiple precast concrete products, and accelerated bridge construction (ABC) methods. This important work was generated out of necessity—the redevelopment of a former brownfield in the area was projected to increase daily traffic on the bridge’s off ramp from 55,000 vehicles to 65,000 vehicles, exacerbating a preexisting issue with stopped motorists on the structure. The project, which would reduce the three existing lanes down to two during construction, needed to be completed quickly, as it would temporarily cause even more congestion in the area. The team, which included Brayman Precast of Saxonburg, Pa., local engineering firm SAI Consulting Engineers, and the Pennsylvania Department of Transportation, met the project’s tight timeline thanks in large part to the precast concrete components specified, which included foundations supported by drilled micropiles, substructure stem and backwall elements, and deck panels.
As Easy as ABC
With speed and efficiency being key considerations for the project, the ABC approach rose to the top. Jake Daugherty, quality control manager with Brayman Precast, noted that the significantly reduced construction time associated with ABC leads to a variety of other positive outcomes, including improved safety and fewer hazards for the public, who would otherwise face complex and lengthy road closures and delays.
“ABC also decreases the risk of weather-related impacts, since the precast concrete elements are cast indoors in a temperature-controlled plant, ensuring enhanced quality control,” Daugherty said. “Fewer road closures and traffic delays are also good for the environment, as there is less idle time for cars in traffic jams.”
Jason DeFlitch, PE, DBIA, project manager for SAI Consulting Engineers, agreed with Kemper, noting that because the precast concrete elements for the bridge substructure could be erected ahead of the interstate closure for superstructure work, significant time was shaved off the construction schedule. Compared with a cast-in-place concrete project, the use of precast concrete and ABC methods reduced the overall project time from 45 days to just 15.
“Precast construction overcame all project challenges, including maintaining two lanes of traffic on I-376 westbound at all times, limiting lane restrictions on adjacent facilities, minimizing utility impacts, and increasing safety,” DeFlitch said. “Minimal crews were needed for construction, and the duration of the proximity of those crews to live traffic was limited.”
The installation of the micropiles and precast concrete substructure elements was completed during weekend closures of the road below the bridge, along with various ramps to and from the interstate. Superstructure widening included a partial removal of a portion of the existing bridge deck, erection of a new girder on substructure extensions, placement of precast concrete deck panels that connected to the existing deck with a longitudinal UHPC closure pour, transverse UHPC pours between adjacent precast deck panels, and placement of precast concrete approach and moment slabs. Overall, the project deployed 27 yd³ of UHPC and $840,000 in precast concrete products, leading to a solution that not only mitigates traffic in the area but also leverages innovative construction methods to enhance safety.
“Widening this westbound bridge on I-376 represents a significant infrastructure improvement that positively impacts the community,” Daugherty said. “Widening and elongating the exit ramp results in a more gradual, smoother exit from the highway, making the driving experience safer for motorists and reducing congestion.”
Mason Nichols is a Grand Rapids, Mich.-based writer and editor who has covered the precast concrete industry since 2013.