Macroscale modelling of the orthotropic shear damage in the dynamics of masonry towers by RBSM

The peculiarity of a rigid body-spring model (RBSM) is exploited to predict and explain a specific damage pattern and failure that is often observed in ancient masonry towers subjected to seismic events. In fact, the full understanding of the frequent appearence of a vertical pattern of cracks along the height of these buildings, which could be viewed as a macroscopic mode II shear fracture, would require to overcome the macroscopic approach based on the standard Cauchy solid continuum. The research focuses on the orthotropic shear response of the masonry material, related to its bond/texture pattern, which is here accounted by a RBSM that allows to assign, heuristically, a different shear strength and internal friction, parallel and normal to the plane of the mortar bed joints. This specific feature, in the context of a set of full dynamical analyses, appears to be a key to predict the crack pattern and failure of an idealized masonry tower, in accordance with the surveys of real towers subjected to strong ground motions.