Effect of specimen size on fracture energy and softening curve of concrete: Part II. Inverse analysis and softening curve

The size effect of fracture energy was observed in experiments presented in the preceding paper. In this paper, the softening curve representing the relationship between the crack opening and the gradual stress drop after tensile strength was found for each specimen of the experiments by an inverse analysis. The effect of the size-dependent fracture energy on the softening curve was then investigated. It was found that the first steep branch of the softening curve is very similar for different size specimens whereas the tail of the curve becomes longer with increased specimen size. The observed size-dependent fracture energy can be explained by the features identified on the softening curve, and a possible mechanism of the fracture process zone with respect to the size effect is discussed herein.