SEISMIC RETROFIT PRACTICE. IN: BRIDGE ENGINEERING: SEISMIC DESIGN

Until the 1989 Loma Pieta earthquake, most of the United States had not been concerned with seismic design for bridges, although some 37 states have some level of seismic hazard and there are numerous bridges that are not adequate for the seismic forces and displacements that we know today. This paper reviews the success of the bridge seismic design and retrofit program as well as the success of the future seismic design for California bridges that is based on the accelerated and problem focused seismic research program of the California Department of Transportation (Caltrans) that has provided the bridge design community with the assurance that the new specifications and design details perform reliably and meet the performance criteria. Discussed in the paper is the bridge seismic retrofit philosophy and procedures practiced by the California bridge engineers. Issues addressed here can be of great benefit to those states and countries that are faced with seismic threats of lesser magnitude, yet have little financial support for seismic retrofitting and much less for research and seismic detail development.