A stress-state-dependent continuum damage model for concrete based on irreversible thermodynamics

The paper deals with an anisotropic continuum damage model for plain concrete to provide an efficient macroscopic approach suitable for boundary-value problems involving nonlinear behavior. The thermodynamically consistent model is based on kinematic description of damage. The Helmholtz free energy function is introduced leading to an elastic constitutive equation which is affected by damage modeling deterioration of elastic material properties. A damage condition is proposed characterizing onset of damage whereas irreversible deformations and volume increase are reproduced by a damage strain tensor. Different branches of these criteria are considered corresponding to different damage mechanisms depending on stress state. Identification of material parameters is discussed in detail. A comparison of results from numerical simulation with available data from different literature experiments demonstrate the efficiency and the applicability of the proposed phenomenological framework.