LOCALIZING GRADIENT DAMAGE MODELS FOR THE FRACTURE OF QUASI-BRITTLE MATERIALS

Abstract

This thesis focuses on the development of an improved gradient enhancement that fully regularizes the strain softening behavior of continuum damage models, i.e. a mesh independent structural response, with the development of localized damage profiles resembling macroscopic cracks at failure. The overall strategy is to first consider an idealized problem, where a higher-order microforce balance governing the damage process is recovered through a novel homogenization framework. Motivated by the insights obtained from the micromechanical analysis, a localizing gradient enhancement is developed from the generalized micromorphic framework, which is shown to avoid the anomalies associated with the conventional nonlocal approach. Finally, an isotropic damage model incorporating a newly proposed equivalent strain measure, regularized with the localizing gradient enhancement, is adopted for the mixed-mode fracture of concrete。