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    Prefabricated Bridge Elements and Systems

    Prefabricated Bridge Elements and Systems (PBES), an Accelerated Bridge Construction (ABC) method, are manufactured offsite, and then transported and assembled at the bridge construction site. This technique shortens construction schedules and helps ensure consistency in product quality. PBES is a Federal Highway Administration (FHWA) Every Day Counts Round 1 (EDC-1) innovation that Pennsylvania championed. 

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    bridge deck being lifted into place.

    How Does It Work?

    With PBES, concrete placement and curing, steel reinforcement and formwork removal can all be done offsite under controlled conditions, and once completed, the materials are transported to the site and installed rapidly. Prefabricated systems are rolled, launched, slid, lifted, or otherwise transported into place, ensuring that no separate construction phase is required after placement. Due to the manner in which they are installed, prefabricated systems often require innovative planning, engineering design, and high-performance materials. 

    Prefabricated deck elements reduce the need for traditional deck construction tasks, including onsite deck form installation, overhang bracket and formwork installation, reinforcing steel placement, set up of paving equipment, concrete placement, and concrete curing. Prefabricated beam elements are composed of two types: "deck" beam elements and "full-width" beam elements. Deck beam elements eliminate conventional onsite deck forming activities and are typically placed in an abutting manner. Full-width beam elements are typically rolled, slid, or lifted into place to allow deck placement operations to begin immediately after site preparation. 

    What Are The Benefits?

    PBES decreases congestion and reduces onsite construction time as the materials are built offsite and built concurrently before being rapidly installed at the bridge location. Fewer delays and road closures also lead to cost savings and increased work zone safety, due to fewer workers being exposed to moving traffic for a shorter period of time. 

    Bridge deck being put into place.

    Innovation in Motion

    PennDOT District 11 used several ABC methods, including PBES, on the replacement of the Shaler Street Bridge over U.S. Route 19 in Allegheny County. Because U.S. Route 19 carries approximately 27,000 vehicles per day and provides connection and access from uptown Pittsburgh to the airport, Heinz Field, PNC Park , and suburbs, the district knew minimizing closures during this bridge replacement project was necessary. PennDOT District 11 chose to use PBES for consistency in product quality, in addition to reducing road closures. 

    To make the short-term closures possible, the new bridge beams and deck were assembled at a nearby site off of U.S. Route 19’s mainline while demolition of the old bridge took place. The components were then moved onto the new support structures using Self-Propelled Modular Transporters (SPMT), which was the first time this technique was used in Pennsylvania. SPMT uses a combination of multi-axle platforms operated through a computer-controlled system. SPMTs are motorized vehicles that move at slow speed and are capable of carrying large structures from offsite locations, positioning them precisely into final position. PennDOT opened U.S. Route 19 to commuters in four days, much more quickly by utilizing ABC techniques.