The seismically vulnerable eastern spans of California's San Francisco-Oakland Bay Bridge are being replaced with a dual, 3.6-km-long parallel structure. The skyway section, which consists of 2.1-km-long twin viaducts, is under construction by a joint venture of Kiewit, FCI, and Manson. The viaducts are precast segmental bridges erected in balanced cantilever, with a typical span of 160 m. The foundation consists of six 2.5-m-diameter pipe piles 100 m in length with a steel pile cap that is in-filled with concrete. The precast segments for the superstructure, which are as heavy as 7 MN, are lifted into position with self-launching winch lifters and are posttensioned. The bridge is situated between the Hayward and the San Andreas Faults, which can generate large earthquakes. Performance criteria require the bridge to be operational after a 1,500-year-return-period earthquake from either of these two faults.
Abstract