Aftershock Intensity Measures And The Damage Potential Assessment

The past earthquake events show that a major earthquake is commonly followed by numerous aftershocks.The mainshock-damaged structure cannot be well repaired before aftershocks due to short time interval.Therefore,there will be a additional damage due to aftershock for the mainshock-damaged structure,which can even cause structural collapse.However,the current seismic design codes only consider individual earthquake events without accounting for the potential risk of aftershock.Therefore,It is necessary to assess the damage potential due to the joint excitation of mainshock and aftershocks.To do this,it is required to evaluate the correlation between the intensities of mainshock-aftershock sequences and structural damages.In light of this,this thesis comprehensively examine the correlation.The main contents can be summarized in the followings.1)A total of 622 real mainshock-aftershock sequences were chosen as earthquake inputs.A group of 21 ground motion parameters were adopted as the intensity measures of main shock and aftershocks.The relationship between main shock intensities and aftershock intensities was examined.2)The Park-Ang damage index was used as structural damage indicator.The nonlinear Single Degree of Freedom(SDOF)system was taken as study case.The cumulative damage and incremental damage of the structure due to main shock-aftershock sequences were analyzed.The linear and rank correlations between the intensities of main shock,aftershock and main shock-aftershock compound intensity and the structural damages in terms of cumulative damage,incremental damage and damage ratio of incremental damage and cumulative damage were comprehensively examined.3)The effects of hysteretic behaviors of nonlinear SDOF systems on the above correlation results were examined.The results show that the compound intensity in terms of the ratio between aftershock intensity and main shock intensity well correlate to the structural cumulative damage and incremental damage.The effect of hysteretic behavior of nonlinear SDOF system on the correlation results is limited and can be ignored.