Non-linear behaviour of masonry walls: FE, DE & FE/DE models

Nonlinear behavior of masonry panels is a topic of great interest in the civil engineering and architecture fields. Several numerical approaches may be found in the literature. Here, three different models are presented and compared to investigate nonlinear behavior of in-plane loaded masonry walls: Discrete Element (DE) model, combined Finite/Discrete Element (FE/DE) model, Finite Element model based on a total rotating strain smeared crack approach (FE-TRSCM). Hence, analysis of masonry is carried out at different scales to compare reliability and application fields of the models. The DE and FE/DE models adopt a micromodeling strategy based on discrete cracks, blocks modeled as independent bodies and mortar joints as elastoplastic Mohr–Coulomb interfaces. These approaches already turned out to be in good agreement for in-plane nonlinear analysis. Here, the FE/DE model adopts hypothesis of infinitely resistant and deformable blocks, with cracks occurring only along mortar joints. Deformability is assumed in the triangular FE domain discretization and embedded crack elements may be activated whether tensile or shear strength is reached. The FE-TRSCM follows a macromodeling approach based on the smeared crack theory, often adopted for concrete. Masonry is modeled as a homogeneous material, with a yield criterion based on fracture energy accounting for masonry softening response on compression and tension. Three approaches are compared and calibrated by reproducing experimental tests on masonry panels in compression and under an increasing shear action. The parametric analyses show the capacity and limit of local micromodels or continuous diffused model to represent masonry behavior.