Seismic Retrofit Design of Long-Span Bridges on Metropolitan Expressways in Tokyo

Abstract

The seismic retrofit design of large cable-supported bridges in Tokyo, namely, Rainbow Bridge, Yokohama Bay Bridge, and Tsurumi Fairway Bridge, is described. The site-dependent far-field ground motion due to a possible maximum credible earthquake was calculated by using a fault rupture model together with the wave propagation technique. The nonlinear seismic responses of the bridges, including the soil-structure interaction, were computed, and it was found that all three bridges may suffer considerable damage. A careful retrofit design was prepared for the structural elements that would receive severe damage. Because large bridges are complex structural systems, an increase in the structural redundancy and the use of the fail-safe concept in the retrofit design are emphasized.