GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 2.2 281 The approach foresees, for each of the identified typology, a preliminary analysis finalized to identify, on the basis of a qualitative approach, the most probable out-of-plane mechanism of each building (Saccucci et al. , 2019, 2021). In this context, the URMbuildings of the historical center of Sora (Fig. 1) have been divided in two typologies, MUR 1 and MUR 2, which mainly differs in terms of age of construction and type of masonry, as reported in Tab.1. Tab. 1 - Characteristics of the building typologies identified in the historical centers of Sora. Building typology MUR 1 MUR 2 Type of masonry Irregular masonry with rough stones Regular masonry with square stones Age of Construction <1860 1861-1945 Number of floors 2-4 2-4 Average floor height 2.5-3.49 m 2.5-3.49 m Specific Use Residential use, storage use Residential use, commercial use, storage use Slabs Timber floors Hollow core concrete Roof Gabled roof Gabled roof and flat roof Materials of the roof Timber and reinforced concrete Timber and reinforced concrete On the basis of this preliminary analysis, the building typologies have been divided into categories, each one characterized by the same type of failure mechanism and the same number of floors. Subsequently, for each category, a virtual set of 3000 buildings has been generated through aMonte Carlo procedure, by varying the geometrical parameters that affect the out-of-plane behavior (wall thickness, story height, percentage of holes in the façade) and the masonry specific weight. In particular, the values of the geometrical characteristics have been generated by considering a lognormal distribution with the mean and the standard deviation derived from the collected data of the building typologies; the values of the masonry specific weight have been generated by considering a uniform distribution, assuming values that vary in the range suggested by the Italian code (Circolare 2019-Tab. C8.5.1). Then, for each virtual building the proposed approach consists of the following steps: - performing a non-linear kinematic analysis in order to evaluate the capacity curve of the considered mechanism under the following hypothesis: rigid block, no-tensile strength, limited compressive strength (Lagomarsino and Resemini, 2009) and absence of sliding between blocks; - assessing, for each damage limit state DS i , the corresponding damage thresholds, C DSi , representative of the capacity of the mechanism; - applying the Capacity Spectrum Method (Freeman, 1998) to define the maximum displacement demand for each damage level, D DSi ; - evaluating the Damage Indexes, DI DSi , i.e. the ratio between the maximum displacement demand, D DSi , and the damage threshold, C Dsi , for each damage level. The procedure ends with the derivation of the fragility curves for each identified category. Regarding the damage thresholds, the first limit state is achieved when: C DS1 =d y (1) where d y is the spectral displacement corresponding to the intersection between the capacity curve of the mechanism and a pseudo-elastic branch that describes the response of the structure until the activation of the mechanism (Circolare 2019). The second limit state is defined by the following damage threshold: