Evaluation of vertical irregularity effects of historical masonry buildings through a simplified procedure: the case of Florence city center

Masonry buildings constitute a large part of the European building heritage. This building stock often presents plan or vertical irregularity generally caused by the architectural and structural modifications undergone over the time. In the context of historical city centres, the most recurring irregularity is the vertical one, due to sudden variations in mass, stiffness (and strength) of walls along the building height. In particular, in the case of Florence city centre (Italy), vertical irregularity is caused by the removing of large portions of masonry walls at the ground floor as a consequence of the changed use of these parts of the building; the functional modification of the openings scheme at the different levels of the building due to the internal renovation of the flats; the rooftop addition. In this paper vertical irregularity in historical masonry buildings is investigated through the analysis of single masonry walls. A simplified numerical procedure is adopted in order to evaluate the influence of vertical irregularity on the seismic response of masonry walls along the building height. The masonry structure is modelled through an assemblage of rigid and infinitely strong blocks, linked in-between and to the soil by means of deformable joints. Numerical results demonstrated that this simplified procedure is able to predict the behavior of masonry walls both before and after the typical structural modifications which involved, particularly, the historical buildings of Florence city center. This simplified procedure is suggested as a useful tool for both research purposes and professional practice.