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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possible overestimation of seismic fragility at lower intensity measure values. For more details, see Del Gaudio et al., 2021, Scala et al., 2022 and Scala, 2022. As briefly explained in the previous paragraph, the form adopted in the post-earthquake survey allows to assign to each building belonging to the damaged DB structural-geometric characteristics (such as the quality of the vertical walls, the kind of the horizontal structures, the presence of retrofit interventions, the number of storeys, …), in addition to the construction age. As deeply investigated in the literature (e.g., Zuccaro et al., 2015), the seismic behavior of masonry buildings is affected by several building’s features, among those the structural typology could mostly modify the building performance under seismic actions: for example, possible disaggregation of the masonry walls could occur in case of vertical structures made of raw stones or rubble. The AeDES form classifies the vertical structures in two types: bad quality (BQ) and good quality (GQ) masonry buildings. The first ones, typically characterized by an irregular layout, are constituted by rounded stones (or pebbles) and/or raw stones (or rubble) with or without courses. Conversely, good quality (GQ) masonry buildings are characterized by a regular layout, constituted by natural hewn stones with or without courses or/and artificial stones (bricks). Moreover, four horizontal structures (vaults, flexible-, semi-rigid- and rigid slabs, respectively called V, F, S and R) are present in the Section 3 of the form. It should be noted that the AeDES form allows to the surveyor to select at most two combinations of vertical and horizontal structures to fully describe the entire building: for example, buildings with vaults on the ground floor and wooden floors (with simple or double plank) in the upper floors are very widespread.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

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Vaults Flexible Slab Semi-rigid Slab Rigid Slab Horizontal structure:

Vertical structure:

Good Quality (GQ) Bad Quality (BQ)

2.5

2

1.5

e λ (g)

1

mean damage

0.5

0

Construction age

Construction age

(a)

(b)

Fig. 1. Mean damage (a) and median PGA deriving from lognormal vulnerability curves (b), given the construction age (Scala et al., 2022).

In the present work, in order to limit the number of classes resulting from the combination of vertical and horizontal structures, a statistical test has been used to compare their damage probability matrices (DPMs) and, if necessary, to merge the classes with similar DPMs. The similarity between classes has been investigated by means of the Wilcoxon rank sum test (also called U-Test), comparing two by two the DPMs of all possible structural classes and leading to the definition of the proposed structural typology classification. As result, horizontal structures are classified in only two types: HS1, which includes buildings with vaults at each floor, vaults combined with other type of slab (in particular, flexible ones) and flexible slabs at each floor; HS2, which includes buildings with semi rigid and rigid slabs at each floor. Such classification confirms the damage and vulnerability trends (see Fig. 1) obtained in Scala et al., 2022, where the same database has been used. With reference to the damaged DB, Fig. 2 shows the distribution of two of the main building’s features for the considered four structural typologies (i.e., BQ/GQ-HS1/HS2), limiting the DB to the only highly populated classes. In general, so-defined buildings classes are differently populated: thus, the generic class is assumed to be representative only when populated with at least 100 buildings (Rossetto et al., 2013), discarding from following elaboration all remaining buildings. Moreover, in Fig. 2 only not-retrofitted buildings have been considered: the presence of retrofit interventions could modify the damage attitude of a given structural typology (Del Gaudio et al., 2021), thus in order to prevent any possible bias in the following fragility assessment, all retrofitted buildings are discarded from the study database. Thus, in Fig. 2 the number of buildings for each possible structural combination typology is provided, given the construction age. As