Analytical Investigation of Bridge Seismic Vulnerability in Wenchuan Earthquake

In order to evaluate the seismic loss risk of highway bridge systems in Wenchuan area, Sichuan, China, statistical seismic vulnerability models of bridges were established based on the collected bridge damage data from the Wenchuan earthquake. A modified Wenchuan earthquake attenuation model was developed for estimating the ground motion parameter, i.e., peak ground acceleration (PGA), at various bridge sites. Two-parameter lognormal distribution functions were assumed to be suitable for developing fragility functions. Combined with the surveyed earthquake damage data, two different statistical models were then used to estimate the parameters based on the maximum likelihood method, and the bridge seismic fragility curves corresponding to four damage states (including minor, moderate, major, and collapse) were generated. According to the type and configuration of bridges, the surveyed bridge samples were categorized and distinct fragility curves of the sub-sample bridges were established. Goodness of fit test of the statistical results was carried out. The results show that the fragility functions cannot be rejected under the 10% significance level.