New Carquinez Strait Suspension Bridge, San Francisco, California

Abstract

The new Carquinez Strait bridge in California with a total length of 1060m and a major span of 728m is the first major suspension bridge to be built in North America in over thirty years. It incorporates the latest in seismic analysis, foundation design and a state-of-the-art steel orthotropic box girder superstructure. The 1927 bridge was replaced mainly because of modern seismic resistance requirements. The bridge is situated in one of the most active seismic regions in the world. In an extreme event, the bridge should suffer only repairable damage. The superstructure is welded continuously from one end to the other, and is isolated from the towers using only rocker links for supports. These rocker links allow the box girder to swing freely between the tower legs, reducing interaction between the towers and the orthotropic box girder. Because of variable geology including soft clays, claystones, shale and fractured claystones and sandstones, the tower foundations were constructed of groups of twelve piles, each consisting of 3-m diameter reinforced concrete piles cast in driven steel shells. Details of the bridge deck are given.