The existing Dumbarton Toll Bridge was built in 1982, connecting the cities of Newark and East Palo Alto in the San Francisco Bay Area. The initial vulnerability studies conducted by California Department of Transportation (Caltrans) in 2004 indicated that the performance of the bridge during a maximum credible earthquake was uncertain. Earth Mechanics, Inc. (EMI) has carried out the necessary study for the seismic evaluation of the bridge. An extensive field investigation was undertaken both on-land and over-water at the site to develop the idealized subsurface profile along the bridge alignment. According to the probabilistic and deterministic seismic hazard analyses incorporated with new seismic source model and Next Generation Attenuation (NGA) models, a 1,000-year return period spectrum was adopted for the Safety Evaluation Earthquake (SEE) event and a 100-year return period spectrum for the Function Evaluation Earthquake (FEE) event. SHAKE and KIPS programs were used to conduct the seismic response analysis and kinematic soil-pile interaction analysis were carried out at selected piers. From this study, two sets of Acceleration Response Spectrum (ARS) curves were generated for the seismic retrofit of this bridge: one for the Main Channel piers and another for the West and East Approach structures. Other seismic retrofit-related issues are also addressed
