Nonlinear static procedures for the seismic assessment of irregular URM buildings

Earthquakes are the main cause of damage for existing and ancient unreinforced (URM) masonry buildings, but the seismic assessment of the latter is a complex task. In fact, they were usually built without any engineered procedure; in addition, they often present features that distinguish them from new modern buildings such as structural irregularities and diaphragms not rigid in their plane. Then, the mechanical response of masonry further complicates a seismic analysis, in fact it shows a distinct nonlinear behavior already for low horizontal forces.