Gradient-enhanced damage model for cracking and crack closing in concrete.


J. Pamin, A. Winnicki, A. Wosatko, Proc. Int. Symp. Anisotropic Behaviour of Damaged Materials, Eds J. Skrzypek and A. Ganczarski, 23 pages published on CDROM, Cracow (2002).

Abstract

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.

Keywords

gradient-dependent continuum, damage, plasticity, crack closing, concrete