New Carquinez Bridge, Northeast of San Francisco, California: Technological Design Advancements

The new Carquinez Strait Bridge, northeast of San Francisco, California, will be the first major suspension bridge to be constructed in the United States since the second Chesapeake Bay Bridge in Maryland in 1973. It will replace an existing steel cantilever truss bridge, built in 1927, that was found to be seismically inadequate. The new bridge consists of an orthotropic closed steel box girder superstructure, two main cables 512 mm (20 1/8 in.) in diameter, reinforced concrete towers, and gravity anchorages. The design has set a new standard in modern suspension bridge design in the United States, particularly with respect to seismic safety. Some of the key elements of the design that are discussed are the global design loading criteria for long-span suspension bridges, the design of allowable stresses in main cable wire, the state-of-the-art design detailing of critical welded connections, the finite-element analysis approach for the box girder to determine the actual plate stresses and stress concentrations, and the design of the reinforced concrete tower leg sections for enhanced ductile seismic performance.