Seismic Retrofit of San Francisco-Oakland Bay Bridge West Crossing

From the toll plaza on the Oakland shores through the approach structures in San Francisco, the San Francisco—Oakland Bay Bridge, built at a cost of $78,000,000 in 1937, is an engineering marvel that carries over a quarter-million vehicles per day. Because of the different segments of the bridge and their inherent vulnerabilities, retrofitting was assigned to several groups within the California Department of Transportation. Briefly described are the analysis and design of the seismic retrofit of the West Crossing, which spans San Francisco Bay between the city of San Francisco and Yerba Buena Island. From the outset of this project, the goal was to keep the bridge in service following a magnitude 8.0 earthquake from the nearby San Andreas fault. Included in this discussion is a summary of analytical and engineering procedures used to model the seismic behavior and the performance of this complex, important structure. In addition there is some insight into the various levels of analysis that were utilized so that the project-specific performance-based design criteria could be met. Furthermore, there is discussion of how energy dissipation through foundation rocking and the use of viscous dampening devices made the overall design objective obtainable. Finally, there is some discussion on the retrofit details used to ensure compliance with the design criteria.