DSI Post-Tensioning Loop Tendon resolves contractor's one-end access dilemma

Alameda Street Grade Separation Bridge, Los Angeles, CA, USA

The bridge is part of the recently finished, $2.4-billion Alameda Corridor, a rail cargo expressway that connects the city of Los Angeles with the nation's largest port: Los Angeles-Long Beach. The corridor is only 32 km in length but is very environmental and financial beneficial to the communities along the corridor because it eliminates traffic congestion (200 at grade roadway crossings were eliminated) and reduces transportation time from three hours to 30 minutes.

The backbone of the project was a 16 km, 15.25 m wide, 10.00 m below grade trench that includes two rail tracks and one access road. Among several railway bridges crossing the trench is the two-span, Alameda Street Bridge.

Rail tracks that cross the trench at a very large skew required a 106.7 m wide, heavily post-tensioned, and reinforced bridge. The railway department imposed very strict construction requirements, one of which was to eliminate post-tensioning tendons going over the middle pier. DSI proposed to use post-tensioning 180 degrees loop anchorage placed at the pier location inside the top and bottom slab and web box girder. Strands were pushed around the loop anchorage and stressing block-outs were created at the abutment end were two jacks simultaneously stressed the two tendons legs. This arrangement drastically reduced construction time saving the contractor substantial time and money.
The project was started and completed in 2001.