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

Non-linear behaviour of masonry panels is a topic of great interest in civil engineering and architecture fields. Several numerical approaches may be found in literature. Here, three different models are presented and compared to investigate non-linear behaviour 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 field of the models. DE and FE/DE models adopt a micro-modelling strategy based on discrete cracks, blocks modelled as independent bodies and mortar joints as elastoplastic Mohr-Coulomb interfaces. These approaches already turned out to be in good agreement for in plane non-linear analysis. Here, 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. FE-TRSCM follows a macro-modelling approach based on smeared crack theory, often adopted for concrete. Masonry is modelled as a homogeneous material, with a yield criterion based on fracture energy accounting for masonry softening response in 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 micro-models or continuous diffused model to represent masonry behaviour.