The Seismic Response Analysis And Fragility Analysis Of Rc Frame Structure Based On Mainshock-Aftershock Ground Motions

Historical earthquakes have showed that engineering structures tend to experienceaftershocks within a short period following the occurrence of main shock. In this case,aftershocks have the potential to aggravate the damage and even cause collapse ofstructures that have been already damaged by the preceding main shock. However,current seismic codes only consider single ‘design earthquake’ ignoring the influence ofthe aftershocks. Recently, seismic risk and earthquake loss are becoming a hot topic in thecommunity of earthquake engineering. Seismic fragility analysis is used to research theprobability that the damage of structures exceed failure states under certain seismicintensity, which belongs to the seismic risk analysis and can be used to estimate earthquakelosses. The RC frame structures are widely used in China, thus this dissertation willstudy the response and fragility of a RC frame structure under main shock-aftershocksequence-type ground motions. The main contents are summarized as follows:(1) One RC frame with five floors is designed according to the Chinese building codes,then the maximum roof drift, maximum interstory drift ratio, residual drift and improvedPark damage index of the structure have been studied under a number of mainshock-aftershock ground motions. The results indicate that improved Park damage indexcan be more comprehensive reflect the additional structure damage caused byaftershocks.(2) The damage potential of main shock-aftershock sequence-type ground motionsis investigated with the correlation coefficient between ground motion intensity ratioand improved Park damage index ratio of the whole structure. The results have shownthat PGV has the highest correlation with the whole structure damage index DI betweensix ground motion intensity parameters followed by PGA.(3) The fragility analysis is performed for the main shock-aftershock sequence-typeground motions. The influence of aftershock on the fragility results is specially studied.It can be found that the aftershock will increase the fragility of structure in the levels of8%-30%, when the intensity of aftershock is0.5-1.0times of the main shock.