Seismic Waves: Ensuring That When the Ground Starts Shaking, Bridges Can Bend Without Breaking [open pdf - 540KB]
Seismic Waves is a newsletter published by the National Earthquake Hazards Reduction Program (NEHRP). "'[The bridge] felt like it was oscillating a little bit, and we saw the road rise up in front of us before we fell.' 'The feeling is kind of a free-fall feeling at [an] amusement-park ride.' Those were the comments of two survivors of the Mississippi River bridge collapse that occurred in Minneapolis on August 1, 2007.1 Although earthquakes were not involved in that tragedy, they have destroyed highway bridges in the recent past. The Loma Prieta earthquake of 1989 collapsed a freeway viaduct in Oakland, California, killing 42 motorists, and in 1994, the Northridge earthquake irreparably damaged 10 bridges in Southern California. The Minneapolis collapse again spotlighted the costly and potentially tragic consequences of bridge failures. The disaster claimed 13 lives and is expected to cost nearly $400 million. Earthquake-related bridge failures can be doubly disastrous, since they not only endanger drivers during the quake, but also hamper emergency response and recovery efforts afterwards. Since the 1970s, however, engineers have made considerable progress in learning how to reduce the vulnerability of the nation's more than 600,000 bridges to earthquake damage. Now, a major research project funded by the National Science Foundation (NSF [National Science Foundation], a NEHRP agency) through grant award CMMI-0420347 is further advancing these efforts."
National Earthquake Hazards Reduction Program: http://www.nehrp.gov/
Seismic Waves (November 2007)