Damage and failure models for masonry

After a brief survey of the available literature regarding mesoscopic and macroscopic constitutive laws for masonry, two models based on Damage Mechanics and suitable for the analysis of masonry structures are presented. In the first one, masonry is considered a macroscopically orthotropic material. A limit domain, endowed with a suitable hardening/softening law, is defined according to piecewise linear functions; material damage is taken into account as a function of inelastic deformation. The second model is proposed to describe the evolution of damage in masonry subjected to increasing or sustained stresses of relatively high intensity. It is based on the introduction of suitable damage variables in a rheological model. In this, way it is possible to predict not only the deformation of the material under sustained loading, but also its behaviour up to failure under stresses either increasing or constant in time. The numerical results given by these two models appear to be in good agreement with the experimental data related to masonry panels and towers.