Finite Element formulation for nonlinear analysis of masonry walls

The work builds upon previous developments made by the authors in the context of the nonlinear, in-plane analysis of masonry walls. The structural behavior is characterized by phenomena, such as strain localization, damage, and friction, which need to be modeled at fine scales. Fine-scale modeling represents a significant challenge with regards to numerical simulations, due to its computational expensiveness and hard manageability. Generally, it requires sophisticated solution strategies, such as multi-grid techniques, as proposed in 2007 by the same authors, which cannot be effortlessly used in engineering softwares for structural analysis and design.In order to overcome such difficulties, we propose a coarse-scale model, to be employed in standard path-following techniques, based on an assumed stress Finite Element formulation in a context of non-associated plasticity. We obtain the nonlinear behavior by assuming a set of planes on the Element where frictional response can take place, together with tensile and compression limit stress. In this way, we capture the essential features of the nonlinear behavior as described by the more refined models developed in the past, exploiting algorithms widely adopted in elasto-plasticity, and therefore suitable for practical use in the analysis of full scale masonry structures.