Bridges and Seismic Retrofit in California

Abstract

The California Department of Transportation (CALTRANS) started its first bridge retrofit program after the 1971 San Fernando earthquake. After the 1989 Loma Prieta earthquake, a bridge retrofit program was established for all publicly owned bridges in the State of California. This chapter gives an overview of CALTRANS' bridge retrofit from 1971 to date. CALTRANS has developed and implemented a number of structure retrofit techniques for these retrofit programs. These retrofit techniques are used at expansion joints, columns, footings, bent caps, and abutments. Experiences from the last several earthquakes such as Northridge in 1994, Landers in 1992, Cape Mendicino in 1992, Loma Prieta in 1989, and Palm Springs in 1986 demonstrated that both hinge retrofits and column retrofits perform well. Current knowledge in the structural behavior of retrofit bridges is limited. Before a full structure replacement decision can be made, bridges need to be retrofitted to the current seismic design standards to extend a structure's life span. By increasing a bridge's seismic resistance capacity, the travelers can be protected from possible bridge collapse and emergency relief can be ensured after a major earthquake. The chapter also highlights the main components of the seismic retrofit program, traditional retrofit methods, and new technology in retrofit.