ENR California Best Projects 2018 Airport/Transit: Transbay Transit Center Bus Ramps
Transbay Transit Center Bus Ramps
Owner: Transbay Joint Powers Authority
Lead Design/ Structural/Civil Engineer: Arup
General Contractor/MEP Engineer: AECOM
The Transbay Bus Ramps project plays a vital role in San Francisco’s new $6-billion transit hub. The project’s freeway on-ramps and bridges connect Interstate 80 and the Bay Bridge to the transit center.
“It was incredible to see how the team constructed this complex bus ramp in the middle of busy San Francisco,” a judge said. “Planning and logistic challenges were taken into account in a very creative way.”
Crews built 1,700 linear ft of concrete-boxed girder bridges spanning six blocks and five busy streets. Foundations for the bridge sections included 9-ft-dia piles up to 150 linear ft deep. To mitigate the limited staging areas for the pile subcontractors, the team installed slurry lines across several blocks and under streets to allow pumping of drill slurry from the tanks to the pile locations.
The heavy drill rigs required to drill the 180-ft piles for the cable-stayed bridge’s foundation needed to be within 20 ft of the Transbay Terminal excavation. Due to the load restrictions on the shoring wall, the team designed a work platform using crane mats that reduced the load and eliminated the need for an extensive trestle to stage the drilling equipment.
More than half of the falsework for the cable-stayed bridge section was installed over the top of the half-finished terminal building. To allow bridge and building work to be completed concurrently, the team designed unique falsework of nine 90-ft by 36-in-dia steel pipe columns, which were installed down to the mat slab of the new terminal basement.