Simulation of rate dependent fracture in concrete using an irregular lattice model

An irregular lattice model is used to simulate concrete fracture behavior under dynamic loadings. The numerical approach is based on rigid-body-spring networks, in which a visco-plastic damage model is applied to describe the rate dependency. A direct tensile test is simulated at various strain rates, and the dynamic strength increase is obtained in terms of dynamic increase factor (DIF). The DIFs are compared with a previous experimental and empirical study to calibrate the visco-plastic parameters. Next, a three-point-bending test is conducted numerically under impact and slow loadings, where the mixed-mode fracture is set up with a notch offset from the midspan. The rate-sensitive failure features are shown at the two different loading rates, and the rate effect on the failure mechanism is related with the peak load in the loading history. This study provides qualitative and quantitative understandings of the rate dependent failure behaviors in concrete.