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Simulazione di esplosioni e metodologie progettuali per la mitigazione del rischio associato.
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Blast resistance assessment of structures: explicit finite element simulations and fragility analyses
No full textA 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
Fragility analysis for the Performance-Based Design of cladding wall panels subjected to blast load
No full textThis paper presents a probabilistic method to support the design of cladding wall systems subjected to
blast loads. The proposed method is based on the broadly adopted fragility analysis method (conditional
approach), widely used in Performance-Based Design procedures for structures subjected to natural
hazards like earthquake and wind. The cladding wall system under investigation is composed by
non-load bearing precast concrete wall panels. From the blast design point of view, these wall panels
must protect people and equipment from external detonations. The aim of this research is to compute
both the fragility curves and the limit states exceedance probability of a typical precast concrete cladding
wall panel considering the detonations of vehicle borne improvised explosive devices. Moreover, the
limit states exceedance probability of the cladding wall panel is estimated by Monte Carlo simulation
(unconditional approach) in order to validate the proposed fragility curve
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