PSI - Issue 44

Giacomo Lazzerini et al. / Procedia Structural Integrity 44 (2023) 163–170 Giacomo Lazzerini et al. / Structural Integrity Procedia 00 (2022) 000–000

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3. Calculation of fragility curves 3.1. Investigated building stock

The numerical models used for the calculation of fragility curves are: A. 336 models based on known geometries of actual buildings (of which design drawings were available); B. 64 models were derived from a typological analysis of the built environment (Lazzerini 2021). Concerning the A models, three real buildings were chosen (as in Fig. 1), and for each of them, some parameters were varied. For the first building A, 208 models were constructed by varying height, material at the base floor, material at the upper floors, floors stiffness, thickness of inner masonry walls, floors load magnitude and percentage of opening at the base floor. For the second building, 88 models were constructed by varying height, material on base floor, material on upper floors, floors stiffness, floors load magnitude, percentage of opening on base floor. For the third building, 40 models were constructed by varying only height, material at the base floor, material at the upper floors, opening percentage at the base floor, having verified the low influence of the other parameters. Concerning the Bmodels, resulting from the morphological analysis, 64 models were constructed by varying height, material on base floor, material on upper floor, percentage of openings on base floor, percentage of openings on upper floor. Therefore, a total of 400 building models were created on the 3Muri software (2020) and 3200 nonlinear static (pushover) analyses were performed (eight analyses for each building model). The modelling approach adopted is the FME (Frame by Macro Element) method. For the morphological analysis of the building, survey forms were arranged in which easily detectable by sight parameters were reported: the size of the building, the number of floors, and the percentage of openings (distinguishing between longer and smaller sides, ground level and upper levels). Some typical features of the building typology under investigation are the large openings at the ground level (usually garage openings or storefronts) and the presence of floor ties, which, together with the rigid floors well anchored to the walls, give the building a box-like behaviour. Statistical analysis of the building revealed that most of the buildings are three- or four-storey apartment buildings with typical dimensions of about 20 m by 10 ÷ 12 m. As shown in Fig. 2, on the longer side of the plan, the percentage of openings on the ground floor tends to be high with typical values ranging from 30% to 60% (Fig. 2c), while on the upper floors it is lower and lies between 20% to 40% in almost all of the investigated buildings (Fig. 2a); on the shorter side of the plan, on the other hand, the percentage of openings is from medium to low (Fig. 2b, d). a) c)

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Fig. 2: Results of typological analysis: percentage of openings on upper floors on the longer (a) and shorter side (b); percentage of openings at the ground floor on the longer (c) and shorter side (d).