The paper presents a regularized constitutive description for concrete and composites, and its numerical implementation. The model combines the gradient damage theory formulated in the strain space with the Burzynski-Drucker-Prager plasticity theory formulated in the space of effective stresses. Attention is confined to small strains and static problems.
An algorithmically convenient version of regularization is provided by a gradient enhancement in which an additional averaging equation involving the Laplacian of an invariant strain measure is present. This equation is responsible for the well-posedness of the boundary value problem. In the employed two-field finite elements the averaged strain measure is discretized in addition to the displacements.
The attention is focused on the damage-plasticity coupling and the incorporation of a projection operator which accounts for the crack closing phenomenon. The projection operator is a source of strain induced anisotropy in the formulation, despite the scalar damage measure used. It is shown that crack closing requires only a minor modification of the original consistently linearized algorithm. Two-dimensional simulations of the localized deformation of concrete beams under load reversals are shown.
gradient-dependent continuum, damage, plasticity, crack closing, concrete