Addressing Compound Hazards by Using State-Dependent Fragility Functions

Abstract

This study introduces a framework for modeling the evolving vulnerability of infrastructure components subjected to compound natural hazards using state-dependent fragility curves. Fragility-based assessments typically assume static component states and neglect the compounding effects of sequential or simultaneous hazards. In contrast, our approach incorporates a Markovian state transition model where each hazard influences the probability of a component to transition between discrete damage states. These transitions are governed by state-dependent fragility functions within a multi-state component model, defined by hazard-specific transition matrices. The model also supports the integration of recovery processes and accounts for the order and interaction of interdependent hazards. Through a demonstrative use case, we show how compound events and recovery strategies can be incorporated to more accurately assess failure probabilities over time. This framework provides a flexible and extensible method to assess risk under correlated multi-hazard scenarios, ultimately supporting improved resilience assessment for critical infrastructure.