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Antioch Bridge Seismic Retrofit
2010-2012
The Antioch Bridge spans the San Joaquin River, north of the city of Antioch and along State Highway 160. CEC replaced the 82 existing 6-foot-diameter original bearings with new friction pendulum bearings, weighing up to 10,000 pounds each, under the twin steel plate girder spans. The Project involved reinforcing the main steel girders, jacking the bridge, removing and replacing all bridge bearings with seismic isolation bearings, and installing 3.7 million pounds of structural steel cross bracing within the major piers. The cross braces were tied into vertical steel columns up to 140 feet high, which were embedded in cast-in-place (CIP) concrete along the inside vertical faces of the existing tower legs. Detailed sequencing and scheduling were required, including critical long-lead steel fabrication. Steel cross bracing then was installed to stiffen many of the twin-leg concrete towers (the tallest ones, 10 of which are situated over water). CEC assessed constructability challenges, particularly those associated with a major flaw in the shop welding procedure specified for the steel cross-bracing design. Working closely with our steel fabricator and with project and design staff, we were able to agree on procedural and specification changes before the steel components were fabricated and were able to deliver all materials to the job site without delaying the project.
