Seismic Performance Evaluation Of Girder Bridge Considering Pile-soil Interaction

ABSTRACT:Pile-soil interaction is one of the difficult problems all the time in bridge seismic engineering. The girder bridge, one of the most popular bridge types in our country, whose seismic performance is need to be researched. Using pushover analysis and capacity spectrum method to evaluate bridge's seismic performance is proved to be a good way. A report of Federal Emergency Management Agency (FEMA440) introduced this particular method while take the pile-soil interaction into consideration. According to this report, a pushover curve should be obtained by pushover analysis at first, then change this pushover curve into capacity curve while considering the dynamic characteristic of the bridge. And next, a demand spectrum curve could be obtained though change the code response spectrum. Demand spectrum obtained need further conversion in order to make it suitable for the structure's demand. At this process, two attenuation factors are used to calculate the effect of kinematics interaction effects and the foundation damping effects. At last, the performance point of the bridge at earthquake of this level can be achieved to stand for the true breakage. The main works are as following:Firstly, three kinds of pile-soil interaction effects were analyzed referring to the FEMA440 report, and the flexible base effects, kinematics interaction effects and the foundation damping effects were discussed respectively. Analysis whether the method introduced in FEMA440 can be used for calculating the seismic performance of bridges with pile foundation while considering those three effects. The flexible base effects were taken in to consideration by building flexible foundation models to do capacity spectrum analysis. The kinematic interaction effects and foundation damping effects were considered by modifying the seismic demand spectrum.Secondly, based on the researchs of pushover analysis, use SAP2000 program to calculat the girder bridge models at different levels of lateral force modes' pushover analysis curve of the bridge structure.Then a question about how to select the appropriate level of lateral force mode was brought out and discussed based on the pushover analysis results. And then pushover analysis of a whole bridge model was analysed while considering the pile-soil interaction.Thirdly, the capacity spectrum method was summarized, and then introduced several ways about obtaining the seismic demand spectrum. Refer to the method introduced in the FEMA440 report, how to calculate the reduction factos caused by kinematic effects and the foundation damping effects have been introduced in detail. At last, seismic performance evaluation of a real bridge model was analysed by using capacity spectrum method while take the pile-soil interaction into consideration.