Blast resistance assessment of structures: explicit finite element simulations and fragility analyses

A failure of the security system of a community leads to a socio-economic instability and consequently to the decline of the community. Nowadays like in the past, a protective design against man-made attacks is important, especially considering that the Free World is constantly prone to destabilization by terrorism. A protective construction should principally guarantee the maximum reasonable survivability of the occupants. If the prevention strategies of defense fail (e.g. intelligence and police activities), the design for blast offers the only possibility to limit the consequences of an explosion. The resistance of a generic structure subjected to a blast load is measured in terms of collapse resistance, defined as the exceeding of a performance limit. The collapse resistance can be assessed directly by applying the blast demand to the structure (un-decomposed approach) or by decomposing the collapse resistance (decomposed approach) in three components: the hazard mitigation, the local resistance, and the global resistance. In this Thesis the decomposed approach is preferred and methods for a quantitative assessment of the collapse resistance’s components are proposed and applied to case-study structures. Concerning the hazard mitigation, deterministic computational fluid dynamic simulations are carried out for assessing the influence of three crucial parameters determining the severity of the blast load due to the deflagration of a gas cloud. The fragility analysis is carried out in the framework of the performance-based blast engineering, in order to quantify the local resistance of both precast concrete cladding wall panels and steel built-up blast resistant doors. Furthermore detailed finite element simulations are carried out for investigating the behavior of concrete slabs and insulated panels subjected to far-field and close-in detonations respectively. Finally, the global resistance is investigated by two methods that take into account the consequences of extreme loads on structures, focusing on the influence that the loss of primary elements has on the structural load bearing capacity.