A damage-plasticity model for concrete accounting for fracture-induced anisotropy

A material model for biaxially loaded plain concrete is formulated within the framework of multisurface damage-plasticity theory accounting for anisotropic degradation of stiffness and of strength as well as for the modelling of inelastic deformations. For the representation of the anisotropic strength characteristics in cracked concrete a gradual stress release according to a kinematic softening law is considered in the post-cracking regime. This softening model is formulated in a reference frame determined by the primary crack. The ductile behavior of plain concrete subjected to predominantly compressive loading is described by means of an isotropic hardening plasticity model. The algorithmic formulation of the model is also adressed in the paper. The model is investigated by means of several comperative analyses of nonproportional loading paths. As a numerical example, re-analyses of a cylinder splitting test are presented.