Cascading Hazard Analysis of a Hospital Building

Recently multiple-hazards engineering has received more attention when evaluating the capacity and analyzing the behavior of a system that is exposed to more than one type of hazard. In this paper, the principle of multiple-hazards is investigated and a new methodology has been developed to assess cumulative damage of structural elements. The proposed approach is able to combine structural damage caused by sequential hazards through their conditional probability of occurrence. The damage related to each hazard has been evaluated independently. The corresponding physical models associated to each hazard have been used to assess the conditional probability of hazard’s occurrence. The method has been applied to a hospital located in California, US. Three hazards (earthquake, blast and fire) have been analyzed. First, non-linear time-history analyses have been performed using seven ground motions scaled to five different earthquake levels and the seismic response of the structure has been evaluated. The seismic input has damaged the hospital’s power supply (LPG reservoir tank) which has caused a blast. The probability of explosion has been estimated taking into account the probabilities of fuel leakage, fuel concentration, and ignition respectively. A set of twelve blast intensity levels has been considered in the analyses, corresponding to different quantities of fuel content inside the tank. Afterwards, a fire hazard is generated following the explosion, whose intensity level has been evaluated using the compartmental heat flux. The fire effects have been modeled assuming an increment of temperature in the steel frame. The proposed multi-hazard approach can be used for both improving the structural safety and reducing the building life cycle costs to enhance in the end, the resilience of the hospital. Results show that this methodology can be used to provide risk mitigation measures within a more general resilience framework.