Research on standard deviation in the vulnerability analysis of isolated continuous girder bridge

At present, during the structural seismic vulnerability analysis, there are two methods to calculate standard deviation, one method is using the value from HAZUS99 directly, the other one is calculating the specific value according to the response of the actual bridge. But, whether the results of seismic vulnerability analysis from two method are the same or not. Are the difference of these results large or small? And whether using the simple direct value from HAZUS99 can meet the requirement, and be applied into the isolated bridge or not. These problems need to be further studied in detail. In this paper, three isolated continuous girder bridge models were established, nonlinear time history analysis of the bridges were carried on using IDA analysis method, and the seismic demand of the isolated bridge was obtained through the regression analysis. The damage index, namely top drift of bridge pier was determined through the moment curvature analysis and pushover analysis and then standard deviation was analyzed through seismic vulnerability analysis of the bridge pier, the isolated bearings and the overall system. Results show that: most of errors of two methods are more than 10% , and the errors of the vulnerability curve of the components or the overall system respectively obtained from two methods are also larger, which indicate that it is unreasonable to use 0. 5 from HAZUS99 directly during the vulnerability analysis of the isolated bridge when PGA is regarded as ground motion parameters.