State-dependent life-cycle structural seismic resilience analysis incorporating corrosion and aftershock effects: illustrated with a corroded RC frame

The interaction of environmental aggression and seismic events may significantly reduce the seismic capacity, serviceability, and resilience of aged structures. Considering the deterioration caused by corrosion and earthquake events, it is crucial to account for the current structural state in the procedure for assessing seismic resilience. This paper presents an analytical approach for assessing seismic resilience that incorporates the influence of corrosion and mainshock-induced damages. Within this methodology, the conventional structural functionality formula is modified by incorporating a time-variant function that is dependent on mainshock damage states. An aftershock fragility is generated by the grouped damage data. An approach based on the total probability theorem is introduced to estimate the downtime caused by ageing and aftershock loadings. In the downtime estimation process, a color-tagged scheme is employed to differentiate between repair and rebuild scenarios for the damaged building. Subsequently, the seismic resilience can be evaluated using the acquired functionality, fragility, and downtime. The assessment procedure is implemented on a representative reinforced concrete frame structure to demonstrate its applicability. The results indicate that corrosion and aftershocks together cause a considerable drop in resilience index and an increase in downtime. The coupling effect of these two factors on resilience is larger than that of each individual factor. Taking into account the contribution of aftershocks and corrosion, the downtime resulting from structural damage is approximately 2.7 times longer than that associated with the mainshock alone. For the damage state induced by the mainshock, it is estimated that when the mainshock causes moderate damage to the structure, there is an approximate 22% reduction in seismic resilience, which should be considered when evaluating life-cycle resilience. The obtained results underscore the importance of considering aftershocks and corrosion, as neglecting them would lead to an overestimation of seismic resilience.