Cascading Hazard Analysis of a Hospital Building

Recently, multihazards engineering has paid more attention to analyzing the behavior of a system exposed to different types of hazards and to estimate the loss data from cascading events attributed to the primary hazard. This paper investigates the principle of multihazards and develops a new methodology to assess the total damage of structural elements caused by cascading hazards. For each hazard, a physical model is used to assess the conditional probability of exceeding a certain intensity level due to the occurrence of the previous hazard. The method is applied to a hospital located in California subjected to three cascading hazards (earthquake, blast, and fire). Nonlinear time-history analyses are performed using seven ground motions scaled to five earthquake levels and the seismic response of the structure is evaluated. The seismic input produces damage to the hospital's power supply (liquid propane gas reservoir tank), which may cause a blast. The probability of explosion is estimated by taking into account the probabilities of fuel leakage, fuel concentration, and ignition. A set of nine blast-intensity levels is considered in the analyses, corresponding to different quantities of fuel content inside the tank. Afterward, a fire hazard is generated following the explosion, the intensity level of which is evaluated using compartmental heat flux. The fire effects are modeled assuming an increment of temperature in the steel frames. The proposed multihazard approach can be used for both improving the structural safety and reducing the building lifecycle costs to enhance the resilience of the hospital. Results show that this methodology can be used to provide risk mitigation measures within a more general resilience framework. (C) 2017 American Society of Civil Engineers.