Comparative Study on Seismic Fragility Assessment of Self-Centering Energy-Absorbing Dual Rocking Core versus Buckling Restrained Braced Systems under Mainshock–Aftershock Sequences

AbstractA strong mainshock may cause several aftershocks within a short interval. These aftershocks can make buildings damaged during the mainshock more vulnerable to collapse. Hence, it is critical to study the seismic responses of a structure during aftershock events following a major shock. The focus of this work was to investigate the seismic fragility of an emerging high-performance seismic-resistant system—the self-centering energy-absorbing dual rocking core (SEDRC) system—considering mainshock–aftershock sequences, and to compare SEDRC with traditional systems. First, three- and six-story SEDRC systems were designed following the direct displacement-based design method to show comparable maximum interstory drifts compared with those of the three- and six-story benchmark buckling-restrained braced frames (BRBFs), respectively, under the design-basis earthquake excitations. Second, 30 as-recorded mainshock–aftershock sequences were selected. The dynamic analyses and incremental dynamic analyses (IDAs) were conducted to study the seismic responses of the four buildings with the mainshock inputs alone and the mainshock–aftershock sequence inputs. The analysis results show that the designed SEDRC systems and BRBFs can obtain comparable performance in limiting the maximum interstory drifts (MID) responses, whereas the SEDRC systems are more efficient in limiting the maximum residual interstory drifts (MRD). Moreover, the SEDRC systems perform much better than BRBFs in resisting structural collapse. As expected, the aftershocks would increase the MID, but may increase or decrease the MRD of the SEDRC systems and BRBFs. Finally, the seismic fragilities of the designed systems were further investigated on the basis of the results from the IDAs in a probabilistic framework using a joint probability density function with the consideration of both MID and MRD. The advantages of the SEDRC systems in achieving excellent seismic collapse-resistant and self-centering capacity were explored through probabilistic analyses.