ANALYSIS OF DYNAMIC FAILURE BEHAVIOR OF CONCRETE BASED ONTHE MESO-ELEMENT EQUIVALENT METHOD

The dynamic mechanical behavior of concrete has an obvious strain-rate dependency. However, the current knowledge on the enhancement of dynamic mechanical properties of concrete is not well established at present. Based on the random aggregate structure of concrete, the mesh grid was divided by the characteristic element size of concrete. The equivalent constitutive relationship for concrete meso-elements was derived combining the strain-rate effect of material strength, and a three-dimensional meso-element equivalent model of heterogeneous concrete was developed. The dynamic compressive tests conducted by Dilger et al were simulated using a two-dimensional model. Results from the present meso-element equivalent method (MEEM) showed favorable agreement with experimental observations and the results from the random aggregate model, illustrating the accuracy of the present meso-mechanical approach. Under different loading rates, the dynamic failure patterns and the macroscopic mechanical properties of the three-dimensional concrete specimen subjected to uniaxial tension and compression were investigated subsequently. It is found that, as loading rate increases the number of cracks or the damaged region increases, implying that the fracture process at high rates requires more energy demand to reach failure, which is the major reason for the enhancement of concrete dynamic strength.