MODELING AND COUNTERMEASURES FOR UNSEATING OF BRIDGES CAUSED BY SURFACE EARTHQUAKE FAULT IN 1999 TAIWAN CHI-CHI EARTHQUAKE

Abstract

Unseating of girders due to surface earthquake fault was observed in many bridges in 1999 Chi-Chi Earthquake, Taiwan, which has not been considered in current seismic design of bridges. In this research, unseating behavior of bridges is analyzed based on the observed data at Chi-Chi Earthquake, and countermeasures are considered. First, 6 degree of freedom dynamic response model for bridge superstructures is constructed, and is shown to agree with the actual damage. The damage is found to be primarily caused by static fault displacement. Several countermeasures of unseating are proposed and their effects are examined with the same analysis model.