SIMPLIFIED RELIABILITY APPROACH FOR STRUCTURES UNDER IMPULSIVE LOADS

Generally for designing structures under blast loads a deterministic approach is used. The design scenario would cover the possible load conditions that a structure could experience if a detonation occurs; but the probability that the structure will satisfy the design performances for the considered load conditions is unknown. Therefore the reliability of blast resistant structures is vague using the current design practice. Alternatively a performance-based design could be adopted to design blast loaded structures but it requires many Monte Carlo simulations. However a probabilistic design of blast resistant structures can be achieved by a single structural analysis where safety factors are applied to the load and structural resistance. Nowadays safety factors are not defined for structures under blast loads. To cover this deficiency the research presented in this article proposes a safety factor for structural elements subjected to impulsive blast loads. This safety factor is function of both variability and median value of the blast load impulse which are a function of the amount of explosive, stand-off distance and their dispersion. A Monte Carlo simulation can solve this dependence scenario by scenario but generally this approach does not fit the common design practice which uses deterministic analyses (e.g. using SBEDS). As part of the research outcomes presented in this article the dependence of the safety factor from the amount of explosive, stand-off distance and both their dispersion is solved numerically and the results are provided in tables and charts. As proof case a design example using the proposed safety factor is carried out and a Monte Carlo simulation is used to confirm the design. Result of the validation is that the proposed safety factor is appropriate for designing blast loaded structures using the common design practice methods and it can be introduced in design guidelines for blast loaded structures.