The investigation of masonry structures behaviour, considered as Normal Rigid No-Tension material (NRNT) and subjected to loads and settlements, is the principal purpose of the present work. The equilibrated solution is a minimum of the energy and, adopting piecewise-rigid (PR) displacement, a minimization strategy procedure is proposed. Some cases will be analysed to illustrate the numerical performances of the PR approach, pointing out the subdivision into macro-blocks arises naturally in solving these minimization problems, and that the subdivisions into macro-blocks predicted by the proposed approximation procedure, are in good agreement with the ones expected and seen in real masonry structures. In particular two applications on masonry panels with irregular openings are exposed simulating the effect of an earthquake, so that variable horizontal forces are applied to the floor levels. The examples shown that the PR strategy appears efficient in reproducing both the location of cracks and the horizontal collapse load multipliers as well as the related collapse mechanisms.
