Seismic design and retrofit of bridges

The 1989 Loma Prieta, 1994 Northridge and 1995 Hyogo-ken nanbu earthquakes caused major damage to bridges and these events together with the research triggered as a consequence of the earthquakes has led to significant advances in bridge seismic design and retrofitting. This paper presents how this has affected design philosophies and design codes in EC, New Zealand, Japan and USA in recent years, with emphasis on the Japanese experience in the aftermath of the 1995 H-k-n earthquake. Near field ground motion, linear/nonlinear static/dynamic response analyses, treatment of liquefaction-induced lateral ground movement are described. Comparison of design philosophy, design force and ductility requirements are compared among the EC-8, New Zealand, Japanese, AASHTO and Caltrans/ATC-32 codes. Seismic retrofitting which was conducted in Japan after the Hyogo-ken nanbu earthquake over 29,000 reinforced concrete columns is described.