An Orthotropic Fourth-Rank Damage Model for Masonry Structures

An orthotropic damage model suitable for the modeling of orthotropic material, e.g. masonry, under plane stress conditions is presented. In the proposed formulation the natural axes of the masonry are assumed coincident to the principal axes of the damage parameters. Then in each direction two independent damage parameters are used, one for compression and one for traction, allowing the crack closure effect to be adequately described. The shape of the admissible field is a double pyramid with rectangular base where the inclinations of the faces correspond to the internal friction angle of the material. The field of the damaged stress is obtained as an homothetia of the admissible field. A comparison between numerical and experimental results in masonry shear walls shows that, when a macro-modeling approach can be used, the proposed damage model is able to well predict the behavior of masonry structures.