Modeling fracture in masonry

A finite element procedure developed for the study of fracture in concrete is extended for the simulation of tensile and/or shear fracture in masonry. Triangular units are grouped into rectangular zones mimicking brick units with surrounding mortar joints. Fracture is captured through a constitutive softening-fracture law at the boundary interface nodes. The mortar joint, which is a plane of weakness, can be modeled as an interface of zero thickness or of a given thickness. At each nodal location, there exist essentially two nodes, the relative displacement (i.e., crack opening or sliding) of which is related to the conjugate internodal force by the appropriate softening relationship. 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. The inelastic failure properties are divided into those for the mortar joints and those for fracture within the brick units. The inelastic failure surface is modeled using a Mohr-Coulomb failure surface with a tension cut-off. Examples which include: Direct tension, microshear, and three-point bending of masonry panels are used to verify the formulation.