![]() ![]() Owing to the retention of the original structure, the bridge's ongoing maintenance costs would continue to be high. The overall appearance would be little changed. The original cost estimate for this refit was $200 million. There would also be modifications to the lattice beams as are now complete for the western suspension spans. The initial proposal for the eastern span involved the construction of substantial concrete columns to replace or supplement the existing supports. All portions of the old eastern span were considered to be at risk in a large earthquake. Ī 2010 view of the original eastern span in foreground with replacement construction beyond. A more recent (2008) analysis asserts an increased probability of a major event on the Hayward Fault. Estimates made in 1999 placed the probability of a major earthquake in the area within the following 30 years at 70%, although studies announced in September 2004 by the United States Geological Survey have cast doubt on the predictability of large earthquakes based upon the duration of preceding quiet periods. ![]() It was clear that the eastern span needed to be made more earthquake resistant. Analysis of the event completed by internal staff has shown that the bridge was close to a far more catastrophic failure in which either the through-truss or the causeway segment would have dropped from their common support structure. The failure was at the transition between the easternmost through-truss and the westernmost double-deck causeway segment, a location where the inertial response character of the structure makes an abrupt change. It reopened on November 18, 1989, with a new stronger retrofit in place. The bridge was closed for a month as construction crews removed and reconstructed the fallen section. The earthquake measured 6.9 on the moment magnitude scale and while the epicenter was distant from the bridge, a 50-foot (15 m) section of the upper deck of the eastern truss viaduct portion of the bridge collapsed onto the deck below, indirectly resulting in one death at the point of collapse. Little was done to address this problem until the 1989 Loma Prieta earthquake. īackground Collapsed section of roadbed visible above support tower immediately after the Loma Prieta earthquake in 1989īridge design experts have known for over 30 years that a major earthquake on either of two nearby faults (the San Andreas and the Hayward) could destroy the major cantilever span. The replacement span is engineered to withstand the largest earthquake expected over a 1500-year period, and it is expected to last at least 150 years with proper maintenance. This part became the subject of concern after a section collapsed during the Loma Prieta earthquake on October 17, 1989. The original eastern section was composed of a double balanced cantilever span, five through-truss spans, and a truss causeway. The Bay Bridge has two major sections: the western suspension spans and their approach structures between San Francisco and Yerba Buena Island (YBI) and the structures between YBI and the eastern terminus in Oakland. With a width of 258.33 ft (78.74 m), comprising 10 general-purpose lanes, it is the world's widest bridge according to Guinness World Records. Originally scheduled to open in 2007, several problems delayed the opening until September 2, 2013. The span replacement took place between 20, and is the most expensive public works project in California history, with a final price tag of $6.5 billion, a 2,500% increase from the original estimate of $250 million, which was an initial estimate for a seismic retrofit of the span, not the full span replacement ultimately completed. state of California and crosses the San Francisco Bay between Yerba Buena Island and Oakland. The eastern span replacement of the San Francisco–Oakland Bay Bridge was a construction project to replace a seismically unsound portion of the Bay Bridge with a new self-anchored suspension bridge (SAS) and a pair of viaducts. (Restricted to standard trucks by tunnel and other structures) San Francisco and Alameda counties, California, U.S.Ĭalifornia Department of Transportation (Caltrans)Ĭoncrete-steel precast segment viaducts, dual steel orthotropic box beam self-anchored suspension main span, cast-in-place reinforced concrete transition connector San Francisco Bay east of Yerba Buena Island
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