Yuan, Y; (2015) Blast response of structures: limits to deformation and fluid-structure interactions. Doctoral thesis , UCL (University College London).

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Abstract

This thesis investigates the blast response of simple structural components - fully clamped beams and plates - underwater and in air. Experimental work by others have shown that, with increasing loading intensity, these components deform in one of either three modes: mode I (large inelastic deformation), mode II (tensile tearing) or mode III (transverse shear failure). The aim of this thesis is to develop theoretical and numerical models that can accurately predict these damage modes, taking into account the effects of fluid-structure interactions, for both impulsive and non-impulsive blast loadings A fully-clamped ductile beam model is proposed that is capable of capturing large elasto-plastic deformation, progressive damage and failure through detachment from its supports. Predictions by the model were validated against experimental data in the literature and with finite element models developed in this thesis. Parametric studies were also performed to elucidate the effects of loading duration on the mode of deformation and the conditions governing their transition. Numerical evidence on elimination of pulse-shape effects using an effective rectangular pulse loading (Youngdahl's approach) has been provided. The effects of uid-structure interaction (FSI) are investigated for fully-clamped, elasto-plastic beams in deep underwater explosions and intense air blast loadings. The main objective is to understand how the introduction of fully-clamped clamped supports alter existing well known results grounded on rigid, free-standing counterpart; and, to quantify how different modes of deformation affects the impulse and energy transmitted to the structure by the blast wave. Sensitivity analyses were carried out to elucidate the dependence of the results on the beam's aspect ratio and inertial mass. The deformation and failure of fully clamped rectangular plates subjected to blast loading are modelled numerically using finite element method. The numerical results are validated against experimental data. Deformation maps delineating the different deformation regimes for different combinations of blast impulse and aspect ratio are constructed for plates of equal mass. The effects of imposing a finite period, as opposed to a zero-period, pressure pulse upon the deformation mode and maximum deflection are discussed.

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