PSI - Issue 44

Santa Anna Scala et al. / Procedia Structural Integrity 44 (2023) 267–274 Santa Anna Scala et al. / Structural Integrity Procedia 00 (2022) 000–000

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highlighted in several studies (Del Gaudio et al., 2021; Scala et al., 2022; Zucconi and Sorrentino, 2022), the damage attitude of a given structural type generally decreases for more recent constructions, because of improvements in seismic classification, normative contents and construction practices.

GQ-HS1

GQ-HS2

BQ-HS1

BQ-HS2

Fig. 2. Structural typology varying the construction age for not-retrofitted masonry buildings of damaged DB.

Figure 2 confirms, as shown in other studies, that the number of BQ buildings progressively decreases over the time, whereas the use of regular textures (i.e., GQ masonry) is quite widespread in the more recent periods. Similar consideration is about the horizontal structures: in fact, vaults and flexible slab are progressively replaced with more rigid slabs. Moreover, varying the number of storeys, the building heigh and the period of the building change. Thus, different number of storeys could affect the building behavior, especially for what concern out-of-plane mechanisms. Several works (Rota et al., 2008; Donà et al., 2020; Rosti et al., 2020) distinguish between buildings with less than 3 storeys (herein called Low-Rise buildings, LR) and buildings with at least 3 storeys (i.e., Mid-High-Rise buildings, HR). The same classification (shown in Fig. 2) is adopted in this work, showing a distribution substantially uniform with the structural typology and the construction age. Lastly, for what concern the un-damaged DB, buildings are described only in terms of construction age and number of storeys, since they derive from census (ISTAT 2011) data. In order to assign also to these latter a complete structural-geometric description, the percentage distributions given the construction age and the number of storeys of each building features deriving from the damaged DB have been extended also to the un-damaged one, according to the procedure explained in Scala, 2022. 3. Seismic fragility assessment In this section, lognormal fragility curves will be derived for the defined building classes, using the Peak Ground Acceleration (PGA) as intensity measure (IM). Damage observed after the earthquake will be translate into 5+1 damage states (DSs) consistent with the European Macroseismic Scale (Grunthal, 1998), according to the conversion rules of Rota at al., 2008. The obtained lognormal parameters will be analyzed to identify a seismic fragility trend with the construction age and the number of storeys. 3.1. Intensity measure Ground motion characterization is made using ShakeMaps in terms of PGA provided by Italian National Institute of Geophysics and Volcanology and generated through the software package ShakeMap . This latter has been originally developed by the U.S. Geological Survey Earthquake Hazards Program and then, specifically adapted for Italian events by (Michelini et al., 2020), using data from INGV broadband stations and Italian Strong Motion Network. Fig. 3 shows the ShakeMap of the 2009 April 6 th event in terms of median PGA, substantially composed by several iso areas deriving from seismic isocurves with width equal to 0.02 g. It should be noted that survey form used after the earthquake provide the location (longitude and latitude) of each inspected building. Contrarily, being the building’s location not available for un-damaged database (since derived from census data), a single position (i.e., municipality’s centroid) for all building in each municipality has been considered.