A new model for simulating cracks in cementitious composites

A new model for simulating cracks in cementitious composites using embedded planes with local plasticity is presented. In the model it is assumed that the embedded planes of degradation (PODs) can not only undergo separation but can also regain contact, with the state of contact being controlled by a local contact model. A local plasticity model is included to capture permanent relative displacements associated with rough contact between the surfaces of embedded cracks. This model is a significant development of the Craft model developed by the second author, which allows shear contact, or aggregate interlock, behaviour, as well as crack opening/closing behaviour, to be simulated more accurately. A fully consistent tangent stiffness matrix and stress recovery algorithm is derived. The model has been implemented in a constitutive driver program and also in the finite–element program Lusas. The model is assessed against a series of single-point stress–strain paths, and against data from normal-shear and cyclic tests. It is shown that the inclusion of local plasticity significantly improves the accuracy of the predictions of the model when judged against experimental data.