Numerical Method for Mixed-Mode I-II Crack Propagation in Concrete

A crack-propagation criterion is proposed in this paper for mixed-mode I-II fracture in concrete. In this criterion, crack propagation is initiated when the difference between the stress-intensity factor at the crack tip caused by the external force and that by the cohesive stress satisfies the crack-initiation equation. On the basis of this criterion, a numerical method is developed to simulate mixed-mode I-II crack propagation in concrete. To verify the criterion, three sets of experimental data are selected: one is obtained from the self-conducted test and the other two are collected from the literature. The numerical results show that the calculated load versus crack-mouth opening and sliding displacement curves and crack trajectories are in good agreement with experimental results. Therefore, once the mode I initial cracking toughness, elastic modulus, fracture energy, possion's ratio, and tensile strength of concrete are available, the whole mixed-mode I-II fracture process in concrete can be predicted with reasonable accuracy.