3D upper bound limit analysis of multi-leaf masonry walls

A full three dimensional (3D) heterogeneous approach for FE upper bound limit analyses of in- and out-of-plane loaded masonry walls is presented. Under the assumption of associated plasticity for the constituent materials, mortar joints are reduced to interfaces with a Mohr–Coulomb failure criterion with tension cut-off and cap in compression, whereas for bricks a Mohr–Coulomb failure criterion is adopted. Four-noded tetrahedron elements with linear interpolation of the velocities field are used for bricks discretization, whereas possible jumps of velocities at the interfaces between adjoining elements can occur. Triangular elements with linear interpolation of the jump of velocities field are used both for joints reduced to interfaces and internal bricks interfaces. In this way, an improvement of the numerical model in terms of collapse load is obtained. er to test the reliability of the model proposed, two examples consisting of an English bond shear panel and a simply supported rectangular stretcher bond slab are discussed. Results obtained are compared with experimental data available and previously presented numerical models. The comparisons show both that reliable predictions of collapse loads and failure mechanisms can be obtained by means of the numerical procedure proposed and that full 3D models should be employed in presence of loads eccentricities and/or multi-leaf walls out-of-plane loaded.