SEISMIC VULNERABILITY EVALUATION AND RETROFIT DESIGN OF LAS VEGAS DOWNTOWN VIADUCT

This study focused on the seismic vulnerability assessment and development of retrofit methods for Las Vegas Downtown Viaduct. The viaduct was built in the 1960s and, similar to other bridges designed prior to 1970, lacks the necessary details to provide sufficient ductility capacity for dynamic loading caused by earthquakes. Several aspects of the behavior of the bridge were studied both at the system level and at component level. The studies at the system level included pushover analysis of the entire structure and an evaluation of the ductility demand. Another aspect of the system behavior was a study of the effects of incoherent ground motions on the forces and displacements of the bridge. Other segments of the study included the seismic evaluation of the ramp structures, the development of retrofit strategies for single-column bents, and the development of retrofit details for multi-column bents. Several research reports providing the details of the above aspects of the study have been prepared. This report presents a brief summary of the highlights of those studies. The study showed that the majority of the columns are in need of seismic retrofit but the as-built cap beams are adequate. For a thorough evaluation of the seismic demand the effect of incoherent ground motions has to be included. The column and pedestal retrofit methods developed and verified in this study proved to be effective and more economical than standard retrofit. Retrofit design methods are presented for both single-column and multi-column bents.