Prefab Bridge Unit (PBU) Accelerates Connecticut Bridge Construction

Accelerated Bridge Construction (ABC) techniques made it possible to maintain traffic during reconstruction of the Cedar Street Bridge (Route 175) over Amtrak in Newington, Connecticut. Benesch incorporated a Prefabricated Bridge Unit (PBU) superstructure to accelerate bridge and road work while also accommodating the high volume of traffic on this essential east-west route.

The use of PBUs drastically reduced the duration of construction and allowed the bridge to remain open throughout the project. Bridge reconstruction and changes to the roadway profile took place during two 56-hour weekends. Fitting construction into these concentrated windows minimized the impact on the travelling public and local businesses. Because the PBUs were substantially deeper than the existing box beam superstructure, the vertical profile of the roadway was increased by more than a foot. The elaborate design also included the incorporation of specialized post-tensioning details required after partial removal in order to maintain traffic on the remaining precast box beams.

Coordination with Amtrak was yet another important component because the bridge crossed over one of its railroad tracks. Amtrak closed that rail line during each of the 56-hour construction windows. To protect the tracks during demolition and construction, timber mats were placed on top of the rails to prevent damage from demolition debris. A track monitoring system helped to ensure the rails did not shift during construction operations.

The $5 million Rehabilitation of Cedar Street (Route 175) over Amtrak was completed for the Connecticut Department of Transportation (CTDOT) in 2017. Design and construction were completed according to schedule.

The use of this innovative design along with ABC was recognized with an Engineering Excellence Award by the American Council of Engineering Companies in Connecticut (ACEC-CT). ACEC-CT cited the project’s complex design and construction staging as worthy of recognition.