An Improved Local Damage Model with Alternative Equivalent Strain for Quasi-Brittle Materials

This paper presents an enhanced model for damage analysis of materials that exhibit quasi-brittle behavior, with a recently developed alternative equivalent strain. The material state is represented by a damage parameter d ranging from 0 (intactness) to 1 (complete failure). Unlike conventional local damage models, the calculation of damage parameters takes into account both the fracture energy and the element characteristic length. This approach not only helps to alleviate the issue of mesh-dependency but also maintains low computational cost. For better modeling the failure behavior under mixed-mode loadings of quasi-brittle materials like concrete and limestone, where compressive strength is higher than tensile strength, two alternative equivalent strains are adopted based on the Ottosen and the bi-energy norm (bi-E) concept. It has been noted in literature that the evaluation of equivalent strain has influenced the prediction of the numerical model on the growth of the damage zone, especially when mixed-mode loadings are involved. By comparing the proposed approach with existing experimental data and other numerical models available in the literature, the accuracy and efficiency of this method are demonstrated.