Large displacement analysis of masonry structures coupling enhanced virtual elements and damage-friction interfaces

Enhanced virtual elements are coupled with cohesive interfaces to create a numerical tool tailored for large displacement analysis of block structures. The model is particularly suitable for masonry composed of stones or bricks connected with or without mortar. Each masonry block is modeled with a single elastic virtual element (VE), based on a divergence-free polynomial approximation of the stress field within the element, and the corotational formulation recently developed by the authors. These stabilization-free VEs are coupled, for the first time, with damaging-frictional interfaces representing the layers interconnecting the blocks, which are innovatively extended to the large displacement framework. Furthermore, in the context of virtual elements, a novel method is presented to accurately evaluate nodal forces equivalent to body loads when internal degrees of freedom are not available. Some numerical applications are performed to investigate the capability of the proposed formulation to reproduce the response of single masonry elements and more complex structural schemes. The analyses prove that the model reproduces well the main nonlinear mechanisms due to the presence of large displacements and material degradation caused by cracking and friction. Finally, the model potential to handle irregular stone walls is proved through numerical–experimental comparison.