Masonry structures, integral components of architectural heritage, are diffuse worldwide and continue to be interwoven within modern infrastructures. The complex nature of their constituents has driven active research toward understanding their mechanical behavior. Accurately and robustly representing the nature of masonry constituents is essential for structural analysis, design, and preservation tasks. This study adopts an adjustable contact constitutive model recently proposed to simulate bond behavior in masonry assemblages subjected to in-plane shear-compression loading. The adopted contact constitutive model, recently proposed by the authors within the Distinct Element Method (DEM) framework, addresses the intricate behavior of unit-mortar interfaces by employing a piecewise linear softening function controlled by the user to capture the softening regime in tension and shear. Meanwhile, the compressive region of the masonry interfaces is controlled by a compressive cap with a radial return algorithm under the explicit time-marching integration scheme of DEM to implicitly couple the shear and compressive behavior. The performance of the constitutive model was assessed on a set of calcium silicate wall experiments tested under in-plane shear and compression loading and presented a comprehensive variety of failure modes. The experimental and numerical results are compared on each system’s global and local behaviors. The findings underscore the robustness of the proposed contact constitutive model in accurately capturing the complex mechanical response of masonry and highlight its potential for structural analysis and damage prediction of a diverse spectrum of masonry structures.

This study presents a robust contact constitutive model in the distinct element method (DEM) framework for simulating the mechanical behavior of masonry structures. The model is developed within the block-based modeling strategy, where the masonry unit is modeled as deformable blocks with potential crack surfaces in the middle of the bricks, while the mortar joints are defined as zero-thickness interfaces. The modeling strategy implements multi-surface plasticity with damage mechanics, including a tension cut-off, Coulomb failure criterion, and an elliptical compressive cap for the damage in tension, shear, and compression, respectively. Two new features are introduced in this contact model: a piecewise linear softening function for strength degradation in tension and shear and a hardening/softening function to phenomenologically define the compressive damage of masonry composite into the unit-mortar interface. The constitutive model is implemented in commercial DEM software using the small displacement configuration and validated against material and experimental tests on masonry walls subjected to constant pre-compression and monotonically increasing in-plane load. The experimental and numerical results regarding the force-displacement relationship and damage pattern produced by the proposed constitutive model are compared and critically discussed, demonstrating the capability of DEM coupled with the suitable constitutive law in simulating the behavior of masonry structures.