Fracture behaviors of concrete CSTBD specimens by the modified MTS criterion under the condition of compression loading

A group of concrete cracked straight-through Brazilian discs are investigated under the condition of quasi-static compression loading, and the fracture initiation angles and the fracture resistances of pure mode II and I-II mixed mode on concrete are obtained by changing the directions of initial cracks and concrete mix proportion. The predictive fracture resistances of different proportions and crack modes (pure mode II and I-II mixed mode) on concrete can be obtained by the modified maximum tangential stress criterion (MMTS), which is proposed by Ayatollahi et al. The predictive results from MMTS criterion are compared and analysed with those from experiments. Especially, the MMTS criterion takes into account the effects of non-singular stress terms (i.e. the T-stress, A 3 and B 3 from the expansion of Williams series and the higher order terms are ignored) in addition to the singular stress terms around the crack tip. The dimensionless parameters in the expansion of Williams series are calculated from “finite element over-deterministic” (FEOD) method. The size of the fracture process zone is calculated by using Schmidt model containing A 3 term. It is found that the results from MMTS criterion are more reliable compared to those from traditional MTS criterion or GMTS criterion when used for predicting the fracture initiation angles and the fracture resistances of pure mode II and I-II mixed mode on concrete, particularly for mode II dominant loading condition.