Retrofitting Bridges to Increase Seismic Resistance

The 1971 San Fernanado, Calif., earthquake was a turning point in the seismic design of bridges. It disclosed a number of deficiencies in the bridges designed according to AASHTO specifications and common practices at that time. California initiated a program of identifying seismically deficient bridges and retrofitting them to make them more seismically resistant. Retrofit philosophy, prioritizing systems, retrofitting details, concepts, hardware and costs are considered.