Fracture of unreinforced masonry walls under shear

A formulation is presented for the simulation of fracture using a triangular unit constructed from constant strain triangles with nodes along the sides but not at the vertices of the combined triangular unit. The basic triangular units in the formulation are grouped into rectangular zones mimicking the brick units and mortar joints. The model is ideally suited to the modeling of fracture in masonry because fracture usually runs along a horizontal or vertical joint in the mortar or is approximately vertical in the brick unit. Fracture is modeled through a constitutive softening-fracture law applied at the interface boundary nodes. The material within the triangular units remains elastic. The inelastic failure surface is a Mohr-Coulomb failure surface with a tension cut-off. The path-dependent softening behaviour is solved using the solution of a linear complementarity problem (LCP), in nonholonomic incremental rate form within a quasiprescribed displacement formulation. The advantage of this formulation is that branching and interacting cracks can be traced. The model is used here for the study of fracture under shear and compression in unreinforced masonry walls.