The Dumbarton Bridge, which crosses San Francisco Bay, carries over 81,000 vehicles daily. AECOM (legacy Shimmick Construction) performed a seismic retrofit of the bridge involving its main channel crossing section. During the project, crews raised the bridge 5 inches using 300-ton and 400-ton jacks to allow installation of the steel seismic isolation bearings.
Work included structural concrete overlay at 14 existing pier footings; structural concrete improvements to 16 existing pier caps; 16 structural steel jacking frames within the existing steel box girders; six friction pendulum bearings installed at each pier; the replacement of two existing seismic joints; and the retrofit of two existing hinge joints. Improvements were added at both approach trestle structures by installing 28 steel pipe piles, each approximately 75 feet long and four feet in diameter. The piles were connected to the existing structure with structural concrete trestles.
Additional work included drainage improvements by installing a new pumping plant; 2,000 feet of 36-inch drainage pipe and 2,000 feet of sheet pile cut-off wall.
Other work included removal of existing cathodic protection systems; improvements to the existing seismic monitoring electrical systems; miscellaneous electrical and fiber optic cable work; and removal of 2,200 linear feet of the original Dumbarton Bridge (Ravenswood Pier).
The project was completed in 2013.