DEM & FEM/DEM models for laterally loaded masonry walls

The wide amount of historic masonry constructions in Italy and other European countries makes of paramount importance the development of reliable tools for the evaluation of their structural safety. Masonry is a heterogeneous structural material obtained by composition of blocks connected by dry or mortar joints. The use of refined models for investigating the in-plane nonlinear behavior of periodic brickwork is an active field of research. The mechanical properties of joints are usually considerably lower than those of blocks, therefore it can be assumed that damages occur more frequently along joints. Thus, a key aspect is represented by the evaluation of the effective behavior of joints and its reliable description into numerical models. With this purpose, in this contribution, different models are defined to simulate, with an appropriate accuracy, the behavior of masonry: Discrete Element Model (DEM) and a combined Finite Element and Discrete Element Model (FEM/DEM). Models are based on rigid block hypothesis and joints modeled as Mohr-Coulomb interfaces. These assumptions may be suitable for historical masonry, in which block stiffness is larger than joint stiffness, allowing to assume blocks as rigid bodies, moreover joint thickness is negligible if compared with block size. Analysis is performed in the nonlinear field to investigate the behavior of masonry walls subject to lateral loads, in order to simulate their seismic response, with particular attention to the determination of limit load multipliers.