Abstract：The dynamic mechanical behavior of concrete has obvious strain-rate dependency. The effects of loading rate and its sudden change on the compressive failure pattern and the macroscopic dynamic mechanical properties of concrete are studied. Taking the influence of concrete heterogeneity, at meso-scale concrete is treated as a three-phase composite composed of aggregate, mortar matrix and the interfacial transition zone (ITZ) between them. The damaged plasticity theory combined with strain effect is used to describe the dynamic mechanical properties of mortar matrix and the ITZ. It is assumed that the aggregate phase does not damage, and thus aggregate is set to be elastic. A plane concrete random aggregate structure is established by the Monte Carlo method. The dynamic compressive tests conducted by Dilger et al are simulated at first, and the good agreement between the present numerical results and the experimental observations indicates the feasibility of the present meso-scopic approach and the reasonability of the selected mechanical parameters. Subsequently, the material strain-rate effect is discussed, and the strain-rate effects in the concrete meso-scale heterogeneous model and macro-scale homogeneous model are compared and studied. Finally, the influence of the sudden change of loading rate during the softening stage on the failure mode and macroscopic mechanical properties of concrete is analyzed. Some useful conclusions are given.
2014, Vol. 33 
