Multi–Hazard Fragility Assessment of Structures Subjected to Post–Earthquake Fire via Vine Copula Model

ABSTRACT Structural damage under multi–hazard conditions can be considerably more severe than that caused by a single hazard; therefore, it is urgent for researchers to account for the combined effects of different hazards in a computationally efficient manner during structural safety assessments. In this paper, a framework to evaluate the multi–hazard fragility of structures based on the vine copula model is developed. A two–parameter failure criterion is adopted to represent structural failure modes under the combined effects of earthquake and induced fire. A reinforced concrete (RC) structure subjected to post‐earthquake fire is used as an illustrative example to validate the feasibility of the proposed approach. A fire event is assumed to occur in the edge room on the ground story. The evolution of conditional probability density functions of structural responses is derived. The impact of seismic intensity, fire intensity, and concrete cover thickness on structural fragility is evaluated. The results indicate that the proposed framework is capable of accurately capturing the nonlinear relationships between multiple hazard intensities and structural damage. Both seismic and fire hazard intensities have a significant impact on structural fragility. The combined earthquake–fire action results in significantly higher structural fragility than that predicted under single–hazard conditions. A reduction in concrete cover thickness can significantly increase the fragility of RC structures under severe fire exposure.