Seismic assessment of the XX century masonry buildings in Florence: Vulnerability insights based on urban data acquisition and nonlinear static analysis

This paper deals with the seismic vulnerability assessment of modern masonry buildings in Florence, Italy. The work focuses on the XX century masonry structures realized before seismic codes. The research is divided into two main distinct phases: i) the acquisition of the main geometrical and structural information at the urban scale; ii) the selection of a representative model to execute an analytical assessment. The first part of the work represents a cognitive phase based on archive research and the collection of the buildings, which allowed the architectural and structural identification of over 300 structures. The second part of the work represents an analytical phase targeted at deriving fragility curves. A real case study representative of the simple block typology with two apartments per floor and a central stairwell has been selected and a probabilistic framework based on nonlinear static analysis has been performed. The analytical conclusions of the research point out a significant vulnerability of these structures, mainly ruled by a weak-piers-strong-spandrels behaviour. For the Life Safety limit state (SLV), around 40% of probability to having DL4 and 40% reaching DL5 are expected. The paper presents the results in terms of generic outcomes providing indications useful for the uncertainty's treatment and the engineering practice.