This is a post-event investigation project to learn engineering lessons from the Loma Prieta earthquake (October 1989) The Loma Prieta earthquake data will be used to develop a new response spectrum method for analysis of bridges and other multyply supported structures that are subjected to differential ground motion. A frequency dependent correlation model for the support motions of the Bay Bridge, accounting for the effects of traveling waves, attenuation, propogation path, and local soil and geologic structures will be constructed and calibrated. This function will be applied to the response spectrum analysis based on the principles of stochastic processes. The new response spectrum method will be used to investigate the response of the Bay Bridge during the Loma Prieta earthquake and to determine the causes of its failure. Special emphasis will be given to determining the influence of differential support motions on the observed performance of the bridge. The results from this anlysis will be compared with planned time-history analysis of the bridge by a separate research team at Berkeley, thus verifying the response spectrum method. The method will then be used to predict the response of the Ba Bridge to a potential earthquake of large magnitude on San Andreas or Hayward faults. This part will be carried out in parallel with other planned studies of the Bay Bridge at the Universit of California at Berkeley. The investigation will advance the methodology for analyzing the bridge response to multiple-support seismic excitations.
