Life-cycle seismic resilience of deteriorating highway bridges under mainshock-aftershock sequences

Reinforced concrete highway bridges often experience seismic events coupled with progressive deterioration due to corrosion over their lifespan. In many cases, the seismic mainshocks are followed by significant aftershocks, causing cumulative damage that disrupts normal operations and delays the restoration of bridges. Current research however lacks detailed assessment of seismic resilience considering the effects of aftershocks and corrosion deterioration over the lifetime of bridges. This study proposes a methodology for evaluating the life-cycle seismic resilience of deteriorating structures under mainshock and aftershock (MS-AS) sequences. Three multi-span reinforced concrete highway bridges with different geometries are used as benchmarks. A suite of 80 pairs of ground motion sequences is selected for undertaking the resilience evaluations based on the seismic scenarios considered. The Park-Ang damage index is adopted for the purpose of quantifying the cumulative damage. Nonlinear dynamic analysis is used to provide detailed insights into the mechanisms through which the aftershocks affect the cumulative damage. Based on the results, time-dependent system fragility curves under MS-AS sequences are developed in conjunction with a cumulative damage capacity model for the bridge piers. The seismic resilience of the bridges is subsequently assessed under ground motion sequences at different service times, and the effects of aftershocks and corrosion-induced deterioration on the resilience are examined. Finally, the life-cycle seismic resilience of the deteriorating benchmark bridges under MS-AS sequences is evaluated using the suggested framework. It is shown that the influence of aftershocks on the cumulative damage depends on a number of inter-related factors, including the relative mainshock-aftershock intensity as well as the dynamic characteristics of the bridges. The findings highlight the merits of the proposed framework in evaluating the life-cycle seismic resilience of bridges for different hazard scenarios and deterioration conditions.