San Francisco Bay Bridge
In the wake of the devastating 7.0 earthquake to hit Haiti this past week around the world television screens exploited images of crumbled buildings and poorly reinforced structures reminding us of another earthquake prone territory a little closer to home in California which is taking lengths to improve major infrastructure to a prominent landmark- The San Francisco Bay Bridge.
The Bay Area is known for its spectacular bridges,” says Bart Ney, a spokesman for the California Department of Transportation (Caltrans). “It’s part of our DNA, so naturally the aesthetics are a key part of the project.”
Caltrans ultimately decided to create a two-stage bridge, marrying a 1.3-mile Skyway to the first ever single-tower Self-Anchored Suspension (SAS) bridge. This revolutionary new structure hangs 1860 ft. of roadway from a single central tower, with the shorter western side rising from Yerba Buena Island, and the longer eastern side extending to meet with the Skyway.
The U.S. Geological Survey estimates there is a 62 percent chance that a magnitude 6.7 or larger quake will hit the area by 2032. The Bay Bridge is flanked on the west by the San Andreas Fault and on the east by the Hayward Fault — putting it right in the strike zone. Since the new bridge’s design specifications require that it last for 150 years, the engineers had to build in state-of-the-art seismic defenses. The SAS tower, for instance, incorporates deformable structural elements to absorb quake forces, much as a car’s crumple zone takes the brunt of a head-on collision. Thanks to this innovation, the structure should be able to accommodate seismically induced movement of up to 1 yard.
