Design of world's longest single-tower self-anchored suspension bridge; first in US. Largest earthquake load imposed on a bridge.

Weidlinger Associates designed the world's longest self-anchored suspension bridge, with a main span of 385 meters. The bridge, which connects Yerba Buena Island and the viaduct to Oakland, replaces a cantilever bridge that was severely damaged in the 1989 Loma Prieta earthquake. The single 300-foot-high pylon tower stands between the two five-lane roadways; the two main cables and wire rope suspenders drape from the tower and slant over the roadways, connecting to the outer edges of the roadway decks. Anchoring the cables into the roadway deck solved the problem of the Bay mud, which cannot support the concrete anchorages of most suspension bridges. The bridge was designed for a 7.25 magnitude earthquake on the Hayward fault and 8+ magnitude earthquake on the San Andreas fault.

This is the largest public construction contract in California's history and one of the most challenging ever undertaken in the United States. The bridge is architecturally consistent with the twin suspension bridges to the east, the hills on both ends of the structure, and the skyway to Oakland. The design process began with a competition between two bridge types, a suspension bridge and a cable-stayed bridge, developed to a preliminary stage (30%) and compared for earthquake reliability, cost, construction risk, and aesthetics.

The bridge is designed to carry ten traffic lanes or eight traffic lanes and two light-rail tracks. A major challenge was the need to complete the structure before another major earthquake occurs, while maintaining traffic during construction. Weidlinger Associates is subconsultant to TY Lin/Moffatt & Nichol (JV).

Completion Date: 2012
Location: San Francisco, California
Owner or Client: California Department of Transportation (CALTRANS)
Prime Consultant(s): TY Lin/Moffatt & Nichol (JV); MacDonald Architects