A detailed micro-model for brick masonry structures based on a diffuse cohesive-frictional interface fracture approach

In the past decades, the mechanical behavior of brick masonry material has been largely investigated using different modeling strategies, ranging from purely microscopic to purely macroscopic ones. The so-called simplified micro-modeling approaches, in which the behavior of mortar joints and brick/mortar interfaces is lumped in discontinuous elements, are commonly judged as very effective for accurately representing the interaction between the masonry constituents with an acceptable computational burden. However, they completely disregard the competition between brick/mortar decohesion and mortar cracking, whose role is not negligible, especially in presence of sufficiently thick joints and/or high-strength mortars. In this work, a detailed micro-modeling approach is proposed for the nonlinear analysis of brickworks subjected to in-plane loads. Such an approach allows failure to occur at the brick/mortar interface level and/or inside the mortar layer, while keeping the discrete nature of fracture phenomena. For this purpose, a novel diffuse cohesive-frictional interface approach for joints is presented, able to simulate multiple micro-crack onset and propagation along a-priori unknown paths. Suitable comparisons with a simplified micro-model are provided to validate the proposed approach. Moreover, a good agreement with the experimental outcomes is found, thereby assessing the reliability of the present fracture-based detailed micro-model in the numerical prediction of masonry strength under complex loading conditions.