MBTA uses ABC technique to replace bridge

By Chris Spahr

On Friday, November 8, the Massachusetts Bay Transportation Authority used an Accelerated Bridge Construction technique to replace a 102-year-old bridge that carries the Red Line trains over Clayton Street in Dorchester.  Using a Self-Propelled Modular Transporter, a new bridge was moved into place within 24 hours of the old bridge being demolished.

ABC, as defined by the Federal Highway Administration, is “bridge construction that uses innovative planning, design, materials, and construction methods in a safe and cost-effective manner to reduce onsite construction time that occurs when building new bridges or replacing and rehabilitating existing bridges.” MassDOT is at the forefront of ABC technology that prefabricates major bridge components in one location and transports them to the construction site where they will be quickly installed using heavy lifting equipment such as cranes, gantry systems, or SPMTs. These prefabricated bridges have even been moved into place using barges in some locations in the U.S.

While ABC technology has become more common in replacing roadway bridges (14 bridges were replaced on Interstate 93 in Massachusetts over 10 weekends in 2011), the replacement of the Clayton Street Bridge was the first time this technology has been used to replace a bridge in the MBTA system.

Chris Spahr is a Graduate Assistant with SSTI.