Mode I Damage Modeling in Brittle Preloading

A new anisotropic damage model for brittle solid inelasticity is developed to accommodate observed behavior in applications where the preloading effects are involved. The shortcomings of conventional damage formulations using the "cumulative damage parameter" is outlined, and a new formulation based on the concept of "effective damage parameter" is proposed. The rate of the effective damage parameter is obtained from the consistency condition associated with a damage surface. The cumulative damage parameter is still used as a measure of total dissipated energy. Anisotropy, dilatation, and strength degradation due to pre-loading effects are captured within the formulation. The model is illustrated for concrete in both proportional and nonproportional stress paths in mode I.