Dumbarton Bridge Structural Analysis
Location: San Francisco, California
DEA was the prime consultant for a $5 million on-call contract with Caltrans District Division of Structures (District 59) for bridges and transportation-related structures in District 4 (San Francisco Bay Area). This project was Task Order 12 under that contract and had the objective of providing a structural analysis in support of a planned seismic retrofit of the Dumbarton Bridge. The Dumbarton Bridge is the southernmost of the highway bridges that span the San Francisco Bay and, at 1.63 miles long, the shortest. The bridge carries six lanes of SR 84 between Fremont, its eastern terminus, and Menlo Park at the western end.
DEA structural engineers provided a nonlinear static buckling analysis of the bridge’s steel superstructure using the finite element tool Abaqus. In addition, our engineers analyzed dead load, service load, and displacements of bearings. Displacements were provided by Caltrans from a time history analysis of a beam model. Finally, DEA provided retrofit recommendations and re-analyzed the structure to confirm effectiveness of the retrofit.
The analysis focused on the main channel span, which is composed of steel girders. This required obtaining sufficient structure details to achieve a solution accurate enough to capture any critical buckling behavior. Three spans were modeled with shell and brick elements, and an additional three spans were modeled using beam elements to apply proper boundary conditions.