This 300,000 s.f., 900-foot long, four-level intermodal airport transportation structure houses the Bay Area Rapid Transit System (BART) and the AirTrain tracks, platforms and stations; airport elevated roadway system; as well as a pedestrian crossover with moving walkways. The structure sits above five lanes of airport traffic and needed to provide protection against earthquakes of a large magnitude.
- This station is classified as an “essential facility” for the City and County of San Francisco, designed for immediate occupancy following a major seismic event, and adheres to the most stringent of design guidelines – Immediate Occupancy following a Maximum Credible Earthquake. It was the first multi-level transportation structure in the world to be designed for such high seismic performance and marked the highest level of seismic performance ever required for SFO or BART.
- Structural seismic challenges included: deep foundations to support the structure in a bay mud site, San Andreas Fault location, multimodal station which needed to “look” like a building while functioning as an aerial transportation structure, and accounting for thermal expansion and contraction while providing seismic continuity to protect the integrity of the steel rails of the BART system.
- The structure is a ductile concrete frame supported by deep precast concrete piles. Large hydraulic shock absorbers, or “passive dampers,” were employed to protect against the occurrence of a seismic collision or excessive separation between Concourse H and the incoming aerial guideways. Forell connected the damper system to the aerial guideway system and performed a dynamic response history analysis to simulate the connection of the Concourse H structure with the guideways for BART and the AirTrain.