STUDY ON ANISOTROPIC DAMAGE OF CONCRETE MATERIAL BASED ON IMPLICIT GRADIENT MODEL

In a complex spatial stress state, the concrete damage generally exhibits strongly the dependence of the stress direction. The damage variable in a scalar quantity in the implicit gradient model can not describe accurately the invalid question of concrete in a complex spatial stress state. A new anisotropic nonlocal damage model based on the implicit gradient model is constructed by introducing an effective damage matrix. It is proved that the rate equilibrium equations remain elliptic. The finite element program based on the model is presented in a complex spatial stress state. The model is applied to numerical simulation of damage of concrete in a complex spatial stress state. The numerical results show that the model can overcome the pathological mesh dependence and zero energy consuming when the strain-softening phenomenon of concrete material is simulated.