Numerical simulation of fracture in masonry

The prediction of crack propagation during fracture is fundamental to the design of masonry structures. The post-peak or softening response is affected by a localization of strain in the fracturing zone. In this paper, a finite element procedure developed for the study of fracture in concrete in Attard and Tin-Loi (1999), has been extended for the study of fracture in masonry. Triangular units are grouped into rectangular zones mimicking the brick units and mortar joints. Fracture is captured through a constitutive softening-fracture law at the boundary nodes. The material within the triangular elements remains elastic. Following the ideas of Lourenco (1996) and Sutcliffle, et al. (1999), the mortar joint, which is a plane of weakness is modeled as an interface of zero thickness. At each nodal location, there exist essentially two nodes, the relative displacement (i.e. crack opening) of which is related to the conjugate inter-nodal 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 yield properties are divided into those for the mortar joints and those for fracture within the brick units. The yield surface for the mortar joints and brick units consists of a Mohr-Coulomb section and a tension cut-off.