TYLin was the engineer of record for the impressive 2,047-foot-long Self-Armatured Suspension Span (SAS) and the 1.2-mile-long precast segmental Skyway viaducts. Both structures are distinctive components of the new 2.2-mile-long East Span of the San Francisco-Oakland Bridge, also known as the Bay Bridge.
Located between two major California fault lines, the earthquake-resistant East Span is open to traffic as the world’s longest single-tower, self-anchored suspension bridge (main span of 1,263 feet). The mega-project is also the largest public works project in California’s history.
TYLin’s unique design for the 525-foot-tall SAS tower consists of four steel shafts connected by shear link beams, which are designed to protect the load-bearing shafts in the event of an earthquake.
SAS uses a single 4,550-foot-long cable, the longest suspension cable with a loop ever used for a bridge. The cable stretches from the top of the tower and loops back under the western end, with thin suspension cables that attach the main cable to beams under the road deck.
The Skyway is the longest section of the East Span. The double viaducts have wide, side-by-side decks, accommodate a total of 10 lanes (five in each direction) and a steel bicycle and pedestrian path.
TYLin designed the Skyway to have an optimal span length of 524 feet. The viaducts consist of five frames to reduce the number of expansion joints. The frames serve the dual purpose of adapting to sliding while maintaining rigidity to resist seismic movements.
Project highlights:
- From concept and final design to construction support services, TYLin provided bridge construction expertise to the California Department of Transportation (Caltrans) for all phases of the project;
- The lifeline design is engineered to withstand the strongest ground vibrations that engineers can expect over a 1500-year period;
- The TYLin design makes East Span the first suspension bridge without a deck-to-tower connection;
- The project marks the first use of seismic energy-absorbing shear link beams in a cable-supported bridge tower;
- The precast beam segments for the Skyway weigh up to 750 tons each, the largest ever built in the world at the time;
- State-of-the-art articulated tube beams are mounted at the expansion joints between the bridge frames.
