The subject of the present contribution is the post-elastic response of an heterogeneous material assembled according with a “masonry-like” texture. For this composite material, a process of loading out of the linear field causes the strain to localize into the mortar joints in which it is essentially concentrated the main part of the mechanical degradation. Since the texture geometry can play a significant role in this process, then it seems of interest to develop a computational model with the feature of retaining some memory of the internal structure also when describing the damage process at the macroscale level. Our attention is focused on this particular aspect by proposing a specific in-plane “mechanistic” approach named
rigid element model
As first, a typical masonry-like texture has been studied when subjected to two different loading conditions that caused high shear strains in the mortar joints. This was done by means of a finite element model that described the masonry-like texture with a microscale level of detail, in the frame of a standard continuum approach, assuming a Drucker-Prager plasticity model for the material components. The material parameters were chosen with the main criterion of performing numerical analyses which emphasized the impact of the composite texture on the development of the failure mechanisms.
Then, two walls with the corresponding boundary and loading conditions were modelled by the proposed mechanistic rigid element model. The mesh was made by square elements connected each to the other by two normal springs and one shear spring, whose elastic-plastic characteristics were calibrated in order to retain memory of the main texture effects. In particular, the objective was to distinguish the in-plane shear response along the directions parallel and perpendicular to the mortar bed joints, somewhat in analogy with the behaviour of an orthotropic Cosserat continuum [
The preliminar numerical results are promising since they show the capacity of the proposed model to include some micro-structure features of the damage process. This notwithstanding, it is apparent that for application to masonry walls it is necessary to improve the present numerical implementation by considering also the effect of the Coulomb internal friction on the shear strengths along the two orthogonal directions.