Objective modelling of non-linear dissipation mechanisms : application to masonry structures

Masonry constructions represent a significant part of the world's built and cultural heritage. Recent seismic events have highlighted the importance of preserving these structures and assessing their vulnerability to complex stresses. This work proposes to develop a predictive tool that captures the mechanical behaviour of these structures and identifies their weaknesses from a conservation perspective. Based on an analysis of masonry degradation mechanisms observed experimentally in the literature, a nonlinear constitutive model is developed to describe the mechanical response of these structures under variable multi-directional loading. Described in a robust thermodynamic formalism, it offers a macroscopic description of masonry while considering the complexity of this heterogeneous material (anisotropy, damage, dissipation by friction, etc). The mechanical behaviour of masonry exhibits a typical softening phase of quasi-brittle materials, leading to strain localisation at the structure scale. In addition to the classical energy regularisation method, a nonlocal orthotropic integral approach is developed for masonry by introducing three characteristic lengths related to the material's mesostructure. This model is implemented in a finite element code (Cast3M) to analyse the response of structures under monotonic, cyclic and seismic loading.