PSI - Issue 78

Francesco Testa et al. / Procedia Structural Integrity 78 (2026) 905–912

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The Da.D.O. database provides a single macroseismic intensity value for each tower location, along with individual Peak Ground Acceleration (PGA) values for each main seismic event. Following a well-established approach (Carbonari et al., 2019; Rossetto & Ioannou, 2018; Sisti et al., 2023), the PGA used in the analyses corresponds to the maximum acceleration recorded at the tower site from events occurring before the inspection date. 3. Regional fragility functions Damage probability matrices (DPMs) and fragility functions developed for all considered subsets and damage levels are presented in Figures 2 to 5. Fragility curves were derived by fitting a lognormal cumulative distribution to the empirical data using the Maximum Likelihood Estimation method, applied simultaneously across all damage levels. This approach prevents the crossing of curves, maintaining a constant logarithmic standard deviation for all damage states, while allowing the median to vary. Calibrated function parameters are reported in Tables 1 and 2. The results show slightly larger levels of observed damage for the Marche region as compared to the Umbria region, for both damage mechanisms and overall macroelement damage, over the entire investigated range of intensity, particularly up to 0.30g. Similarly, the damage levels observed for Macerata province are greater than in Perugia province. The comparable trends can be justified by the similar statistics between the considered region datasets and the provinces that constitute their main subsets. When comparing the fragility curves, significant differences can be observed in the probabilities of exceeding the damage states for increasing values of PGA. The results for Macerata province show the highest probability of exceedance, slightly larger than that for the entire Marche region. Although towers in Perugia province and entire Umbria region exhibit lower probability of damage exceedance, this trend reverses for some levels of damage and mechanisms at higher PGAs, closer to 0.4g.

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Fig. 2. DPMs as functions of the PGA: (a) Marche region; (b) Umbria region.