Life‐Cycle Seismic Loss Assessment of Aging Infrastructure Subjected to Multiple Mainshock‐Aftershock Sequences and Long‐Term Environmental Exposure

ABSTRACT Probabilistic risk assessments provide a valuable basis for managing the safety and functionality of infrastructure exposed to extreme hazards, where the economic loss is increasingly recognized as a critical performance metric. In seismically active regions, infrastructure systems are frequently subjected to mainshock‐aftershock sequences, while long‐term environmental exposure further exacerbates their vulnerability to seismic events. However, existing frameworks have limited capability to estimate the economic loss of aging infrastructure under multi‐hazard conditions. This study proposes a life‐cycle seismic loss assessment framework for aging infrastructure under coupled mainshock‐aftershock and environmental deterioration effects. In this framework, a hierarchical Markov process is employed to describe the structural state evolution induced by multiple stochastic seismic sequences and long‐term aging effects. Furthermore, time‐ and state‐dependent fragility surfaces are developed to capture the evolving structural capacity under multiple hazard mechanisms, explicitly representing the coupled effects of sequential seismic loading and long‐term environmental deterioration. Finally, a new generalized recovery model is formulated to provide a unified and flexible representation of recovery processes under various resource constraints and repair strategies, enabling a more realistic characterization of partial performance restoration due to incomplete repair actions. A case study on an aging containment structure is conducted to demonstrate the applicability of the proposed Markovian framework. The results show that the consideration of multi‐hazard‐induced damage accumulation and incomplete repairs substantially increases the expected seismic loss, highlighting the necessity of incorporating multi‐mechanism damage evolution when evaluating the long‐term seismic risk of aging infrastructure.