COHESIVE CRACK MODELS FOR CEMENT MORTAR EXAMINED USING FINITE-ELEMENT ANALYSIS AND LASER HOLOGRAPHIC MEASUREMENTS

Unlike classically brittle materials, concrete and mortar toughen as cracks propagate. One of the methods to account for this quasi-brittle response is to use cohesive crack models. Closing pressure, which is assumed to be a function of crack-opening displacement, is applied on the crack faces in such models. In this paper, measurements of crack-opening profiles by laser holography were used to examine the various closing-pressure models. An iterative process based on linear elastic finite-element analysis with singular elements was used to compute crack profiles when the closing pressure was applied to the crack faces. The predicted crack profiles were compared with the experimental values for evaluation. The validity of the assumption of eliminating crack tip singularity was studied. A crack-length-dependent cohesive model is proposed based on experimental measurements of the crack profile.