Failure mechanisms and crack patterns characterizing the nonlinear response of masonry under both vertical and horizontal load conditions are strongly affected by its intrinsic anisotropic behaviour. Moreover, in case of ancient masonry walls, typically constituted by high strength units (stone blocks or bricks) and weak mortar, texture is one of the key elements that determine failure morphological features. Some analogies between this material and fissured rocks can therefore be envisaged: the discontinuities of a rock mass and their orientation drive failure similarly to mortar joints in masonry walls and in both cases cohesion and friction characterize the response along these weakness planes. However, peculiar features such as interlocking due to staggered head joints and the periodic nature of masonry need to be considered and make its constitutive response more complex. In this research work the in-plane and the out-of-plane behaviour of masonry walls are analysed. The adopted constitutive model has been formulated stemming from a pre-existing one, originally conceived to simulate the behaviour of jointed rock layers, and has been implemented in the commercial code PLAXIS 3D. It is a three-dimensional model based on the identification of preferential orientation of failure planes, on which a Mohr Coulomb failure criterion holds in conjunction with a tensile stress cut-off. Elastic properties are derived from a relatively simple homogenization procedure and geometrical characteristics of blocks as well as the effect of staggered arrangement of head joints are accounted for. Some case-studies for different geometrical configurations are analysed. Results are compared with both experimental evidences and the numerical outcomes obtained resorting to a different constitutive model in which masonry is described as a homogenized anisotropic medium. The proposed model is also adopted for the simulation of a real-scale static soil-structure interaction problem, aiming at highlighting the capability of the model to describe the macroscopic behaviour in terms of collapse mechanism and collapse multiplier. In spite of its simplicity, the proposed approach is able to account for the role of texture with low computational cost and a relatively limited number of mechanical parameters.
Sangirardi, M., Malena, M., de Felice, G. (2020). Settlement induced crack pattern prediction through the jointed masonry model. In Lecture Notes in Mechanical Engineering (pp. 1971-1980). Springer [10.1007/978-3-030-41057-5_158].