ON SOME NUMERICAL TECHNIQUES for STRESS-CONSTRAINED CONTINUA

A numerical method is described for the semi-explicit solution of the constitutive equation of an orthotropic non-linear elastic material with various constraints on the stress. Each constraint forces the stress to belong to a closed and convex cone in the space of second order symmetric tensors, and via the choice of appropriate values cones vertex is possible to assign different strength characteristic in different directions. The constitutive equation thus formulated allows to model masonry with very general textures. However application to problems of equilibrium and evolution requires some numerical expedients which are described in detail in this paper. The equation, implemented in the MADY finite element code, has been used to examine how the masonry panel strength changes as a function of traction directions. The results have been compared with the analougous obtained modelling the masonry at the micro scale.