Masonry is an inherently discontinuous material, formed by various components (stones, bricks, mortar), and its mechanical behavior reflects this internal structure. Engineering modeling of masonry structures is often based on continuum representations, using appropriate constitutive models, which provide an adequate solution for many practical cases. However, discontinuum models, which attempt to represent more closely the masonry components, are today applied with increasing frequency. They are preferred in research studies intended at understanding the mechanical behavior of masonry structures, but they are now also applied in engineering analysis, as the progress in computational resources is making them more accessible.
Discontinuum representations may be achieved with various formulations of finite element methods. The present paper focuses on discrete elements models, a designation that covers a variety of representations of a structure as a system of blocks (rigid or deformable) or particles. Simplified contact formulations are generally used, to allow the analysis of very large systems, and explicit large displacement algorithms are employed.
The paper discusses, in particular, two types of discrete element model, in relation to the specific requirements of masonry analysis. The first type is block models (rigid or deformable), which have proved very effective in the seismic analysis of historical stone masonry structures. Several applications are reviewed and key issues arising in this field are addressed, namely the variability of response observed in rigid block dynamics and the simplifications required in the analysis of large or complex structures.
The second type of discrete element models examined is circular particle models, which represent each masonry block as a set of disks linked by contacts with tensile and shear bonds. Particles may also be used to simulate mortar or infill, and contacts between the various components are assigned appropriate constitutive behavior. An example of analysis of a multi-leaf wall is presented. The potential uses of these models in the study of the fundamental mechanics of masonry, in particular irregular masonry constructions, are discussed.