Limit analysis of masonry vaults by means of curved shell finite elements and homogenization

The study of masonry vaults should take into account the essentials of the material “masonry” – i.e. heterogeneity, almost no resistance to tension combined with a good compressive strength and a high friction coefficient, as well as the overall importance of the geometry for achieving the equilibrium.In this paper, a new six-noded triangular curved element, specifically developed for the kinematic limit analysis of masonry shells, is presented. Plastic dissipation is allowed only at the interfaces (generalized cylindrical hinges) between adjoining elements for combined membrane actions, bending moment, torsion and out-of-plane shear, as it is required for the analysis of thick (Reissner–Mindlin) shells. An upper bound of the collapse load is so obtained, since, looking at the dual formulation, the admissibility of the stress state is imposed only at the element boundaries. Masonry strength domain at each interface between contiguous triangular elements is evaluated resorting to a suitable upper bound FE homogenization procedure. The model is assessed through several numerical simulations on a number of masonry shells experimentally tested until collapse. In particular, the dependence of the collapse multiplier on the mesh and on the material parameters (sensitivity analysis) is thoroughly discussed.