Assessing the behaviour of reinforced concrete columns under blast loads

Abstract

This Thesis is concerned with the numerical investigation of the structural response of reinforced concrete columns under blast loads, by means of dynamic nonlinear finite element analysis. This study provides an in depth understanding of the mechanics underlying reinforced concrete structural response under blast loading and studying the effect of certain important design parameters on the exhibited behaviour. The numerical investigation was carried out through the use of a well-established commercial finite element package (Abaqus) and employed a numerical model capable of accounting for the brittle nature of concrete. The latter model forms an extension to the ‘brittle crack’ model (already available in Abaqus) and was developed in order to overcome the shortcomings of the existing concrete model in describing concrete material behaviour in compression. The verification of the validity of the numerical predictions is based on a comparative study with relevant experimental data. The validated models are then employed to investigate the effect of various parameters on the exhibited response and are used to identify the reasons that trigger the experimentally and numerically observed change in structural behaviour under high loading rates (compared to that established under static loading). On the basis of the predictions obtained from the FE analysis a new graphical method was developed, based on building complementary diagrams, for the effective derivation of Pressure-Impulse (P-I) diagrams. This method aims to overcome the problems associated with their inherent sensitivity to any change in the state of the analysed structural system. Through the combined use of the validated FE model and the proposed graphical method, P-I diagrams and the associated complementary diagrams are presented and the efficiency and applicability of the methodology is demonstrated.