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3 Introduction Background As design for seismic motions has matured over the past decades, the single performance goal of avoidance of collapse has more and more frequently been found not to meet the expec- tations of postevent condition by owners, policy makers, and the public at large for a certain subset of the bridge inventory. Because of this and because of advances in seismic engineering that have made the attainment of higher levels of seismic performance practical both technically and financially, a need was identified to provide guidance to designers and owners on how to identify what increased level of performance should be considered and, once identified, how to achieve that performance through the design process. Research Objectives The two main objectives of this research were to develop proposed AASHTO guidelines for performance-based seismic bridge design and updated seismic hazard maps for AASHTO based on the latest U.S. Geological Survey hazard models. C H A P T E R 1
