INCREMENTAL DAMAGE ANALYSIS OF NONLINEAR SINGLE-DEGREE-FREEDOM SYSTEMS SUBJECTED TO MAINSHOCK-AFTERSHOCK EARTHQUAKE SEQUENCES

The incremental damage of nonlinear single-degree-of-freedom (SDOF) systems subjected to real and artificial mainshock-aftershock (MA) sequences is evaluated. A suite of 75 real mainshock-aftershock sequences is selected. Based on the same mainshock records, different methods including the repeated method, the randomized method and the attenuated method are also adopted to generate artificial MA sequences as earthquake inputs. The nonlinear responses of the SDOF systems due to earthquake sequences are calculated considering different hysteretic models, including the elastic-plastic model, the bilinear model considering the post-yielding hardening, and the trilinear model. The modified Park-Ang damage index is used as a structural damage index, and the structural cumulative damages and the incremental damages due to MA sequences are examined by considering the effects of different strength reduction factors, different hysteretic models and different MA sequences. The results show that the aftershock-induced incremental damages of structures cannot be neglected. The aftershock records from the artificial MA sequences generated by the repeated method and the randomized method have stronger intensities than that from the real MA sequences. This may cause the overestimation of the incremental damage of structures due to aftershock. However, the intensities of the aftershock records for the artificial MA sequences generated by the attenuated method are smaller than that of the real MA sequences, which may lead to an underestimation of the incremental damage of structures due to aftershock. The characteristics of structural systems have ignorable effects on aftershock-induced incremental damage since the effects of strength reduction factors and hysteretic models on the incremental damage of structures are not significant.