Modelling of dynamic behaviour of concrete materials under blast loading

Abstract

In order to model the behaviour of concrete structures under blast loading, it is essential to be able to model the dynamic strength and other strain rate dependent properties of the concrete material. In this paper, a constitutive model for predicting the dynamic strength and damage of concrete subjected to blast loading is developed. The model stems from the continuum fracture mechanics of microcrack nucleation, growth and coalescence to formulate the evolution of damage. The concrete is assumed as homogeneous continuum with pre-existing microcracks. Damage to concrete is defined as the probability of fracture at a given crack density, obtained by integrating a crack density function over time. Based on the damage function, the stress response at a particular time, and hence the dynamic stress–strain relationship, can be established for a given strain-rate. The required material constants representing initial crack properties are derived from material dynamic strength tests. Comparison with available test results shows that the proposed model can give consistent prediction of the dynamic behaviour of concrete materials. Nominal fragment sizes of concrete and fracture strain energy are also derived which can be useful in an energy-based concrete break-up and debris throw prediction procedure.