Hybrid Virtual Element Method for the Analysis of Masonry Structures: A Practice-Oriented Elasto-Plastic Approach based on a Multi-Failure Strength Domain
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The analysis of the mechanical response of masonry structures remains a significant challenge due to material heterogeneity and complex failure mechanisms. Although structural-level strategies, such as equivalent frame methods, are favoured in practice for their efficiency, they often struggle with the irregular opening layouts typical of historic structures, where structural idealization is frequently ambiguous. This work proposes an effective Hybrid Virtual Element Method (HVEM) framework for the nonlinear analysis of masonry, providing a robust, material-level description that avoids the need for a priori structural idealization. The proposed approach integrates a hybrid virtual element formulation with a multi-failure strength domain (considering both masonry joint and block failures) to solve a plane stress elastic-perfectly plastic problem. A key feature of this approach consists in the straightforward mechanical characterization of the strength domain, definable by directly using the mechanical parameters available in codes. Plasticity is here considered at the element level through a multi-surface convex optimization problem. The HVEM formulation offers various advantages, including enhanced robustness against mesh distortion and high accuracy even when coarse meshes are used. In addition, the a posteriori-informed identification of ultimate structural conditions can be conducted, so effectively bypassing the limitations of equivalent frame models idealization. The capabilities of the proposed approach are shown through benchmarks on masonry facades featuring regular and irregular opening layouts.
