San Francisco Airport BART Extension

Seismic Evaluation

The BART-SFO Extension begins at the existing Colma BART Station where the project alignment follows the abandoned Southern Pacific right-of-way southward through Colma, South San Francisco and San Bruno.  South of the San Bruno BART Station to Millbrae Station, the alignment parallels the Caltrain commuter rail line.  A 1.2 mile aerial Y-stub (a Y-Shaped track structure) runs perpendicular to this 7.5 mile mainline track across US Highway 101 into the expanded international terminal at the San Francisco International Airport.

SC Solutions conducted the seismic evaluation of all the aerial structures.  The following nonlinear effects were considered:  geometric effects including large displacements and contact/spring elements at the expansion joints, and material nonlinearities implemented in order to characterize the behavior on the rail to superstructure connections and column plastic hinge regions.  Explicit modeling of the rail allowed for the examination of its effects on the overall seismic performance.