Seismic Fragility Evaluation of Soil-pile-structure Interaction Effects Subjected to Mainshock-aftershock Records

In most current seismic design on bridges, only mainshock actions are considered without incorporating the effect of mainshock-aftershock (MA) sequences and interaction soil-pile.However, a large mainshock usually triggers numerous aftershocks in a short period. This paperstudy the effect of mainshock-aftershock sequences on the behavior of interaction Soil-pile-structure system (ISPS). abeam on nonlinearWinkler foundation (BNWF) model is usingand subjected to non-linear static analysis and incremental dynamic analysis (IDA) leading finally to the fragility curves which are developed. These analyses aim to capture the collapse state of structures under aftershock events preceded by various mainshock levels. Results obtained from capacity curve, incremental dynamic and fragility curves of ISSP system.The analytical results show that in the MA sequences,for dense soil the vulnerable of mainshock-aftershock (MS-AS) loading are more damage due to mainshock loading for all diameter of the pile and the mass. For soft soil   are more vulnerable to damage due to mainshock-aftershock (MS-AS) loading.  But in the stiff clay the effect of mainshock-aftershock (MS-AS) loading for all the diameter of pile and  for masse are neglected. Keywords:bridge,interaction soil-pile-structure, Winkler foundation, dynamic analysis, fragility curves,mainshock-aftershock.