A Numerical Model for Multi-Leaf Stone Masonry

This paper presents a non-linear finite element material model for the analysis of the mechanical behaviour of multi-leaf masonry, which is quite commonly encountered in ancient stone masonry buildings. A damage model, previously developed by some of the authors for brittle materials (namely, concrete) was adapted to fit the experimental stress-strain behaviour of stone masonry. To this end, a damage evolution law originally proposed for concrete was modified and a new material parameter was added. A distinguishing feature of this model is that damage is modelled by a second-order tensor, thus allowing oriented ‘cracks’ to be described; the orientation of the cracks is fixed once they are activated, whatever the subsequent stress history be. Then, the modified model was implemented into a subroutine, linked to a commercial finite element code suitable for nonlinear analyses (FEAP). In order to validate the obtained material model, results available from tests on three-leafed stone masonry prisms were employed. The damage evolution law was calibrated according to results obtained from the single layers, individually tested. The numerical nonlinear structural response was obtained by prescribing suitable displacements boundary conditions and employing a tangent stiffness matrix procedure. In nearly all the applications, the finite element analyses predicted the experimentally measured peak load with good accuracy. However, the post-peak behaviour was not always satisfactorily described: this is likely to be attributed to some numerical instability, which will be overcome in a future version of the model.