SELF-ANCHORED SUSPENSION SPAN
If one single element bestows the status of world-class on the new Bay Bridge, it is the Self-Anchored Suspension (SAS) Span. This engineering marvel will be the world's largest SAS bridge (2,047 feet).
The SAS is not just another suspension bridge. Traditional main cable suspension bridges have twin cables with smaller suspender cables connected to them. These cables hold up the roadbed and are anchored to separate structures in the ground. While there will appear to be two main cables on the SAS, there is actually only one. This single cable is anchored within the eastern end of the roadway. The cable is carried over a single tower and wraps around the two side-by-side decks at the western end.
The SAS, and the rest of the new East Span, is being built to the north of the existing bridge. By switching from the existing East Span's double-decks to side-by-side roadways, drivers will enjoy unencumbered and expansive views of the Bay Area as they pass beneath an angled canopy of suspension cables. The SAS, and Skyway, will feature a 15-foot-wide cantilevered bicycle and pedestrian path on the eastbound side of the bridge, so those traveling on foot or two wheels between Oakland and Yerba Buena Island (YBI) can enjoy those majestic views of the Bay as well.
The new SAS bridge echoes the existing towers of the West Span, as well as the towers on the Golden Gate Bridge. All vertical elements of the SAS – the tower, piers and lights – have been designed to emphasize its clean modern lines. Adding to its distinctiveness is the asymmetrical design. The bridge will have a longer forward span (east of the tower), which will provide a more gradual transition from the gently sloping Skyway, and will give the new East Span a unique silhouette. While the new East Span will have side-by-side decks, those decks will transition to a double-deck structure at YBI, to carry traffic through the YBI tunnel and onto the West Span.
The design features state-of-the-art seismic safety elements and will provide the East Span with a modern, streamlined appearance. Rising 525 feet above mean sea level and embedded in rock, the single-tower span is designed to withstand a massive earthquake. The single steel tower will be made up of four separate legs connected by shear link beams, which function in the same way as a fuse in an electrical circuit. These beams will absorb most of the impact from an earthquake, preventing damage to the tower legs. In addition, if one of the legs is damaged, the other legs will keep the bridge standing.
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