PSI - Issue 44

Valentina Buonocunto et al. / Procedia Structural Integrity 44 (2023) 67–74 Valentina Buonocunto et al. / Structural Integrity Procedia 00 (2022) 000–000

69 3

municipality under review, section 2 contains a short description of the building type under consideration, providing various information such as: number of storeys, average floor height, average floor area, age of construction and prevalent use and the section 3 must be completed according to the type of building under consideration (masonry or reinforced concrete). In this study, an investigation of typological-structural information about existing buildings in the areas under study was carried out. This allowed the identification of building archetypes representative of the actual residential buildings, deriving statistical distributions of masonry types, age of construction and number of storeys above ground. Specifically, the most common masonry type in Campania is the regular soft stone masonry (labelled as C1 in the CARTIS database) with a frequency of occurrence of 59%, while observing cut stone masonry (labelled as B2) and irregular rubble stone masonry (labelled as A2) in the remaining 22% and 19% of existing buildings, respectively. In line with a logic tree approach, the exposure data for each masonry type was disaggregated according to the age of construction, number of storeys, and type of floor. Each data subset is then characterized by several geometric properties, such as the average floor area, average inter-storey height at ground floor level, average wall thickness at ground floor level, and average wall spacing. Those data sets were subsequently used to randomly generate the buildings. Figure 1a shows that most of URM buildings located in Campania were built before 1972, whereas more than 80% of buildings were made of either 2 or 3 storeys according to Figure 1b. Single-storey buildings were found to be 17% of existing URM buildings, hence revealing that only 1% of buildings has 4 or more storeys. More in general, such data indicates that URM buildings in the selected region are low-rise constructions.

a

b

0% 20% 40% 60% 80% 100%

0% 20% 40% 60% 80% 100%

% Buildings

% Buildings

1

2

3

≥ 4

No. Storeys

<1919

>1981

1946-1961 Age of Costruction 1962-1971

1919-1945

1972-1975

1976-1981

Fig. 1. Histograms of URM buildings in Campania: (a) year of construction; (b) number of storeys

2.2. Derivation of typological fragility curves

Statistical data sets derived from CARTIS were combined with statistics and distributions for material properties provided by the CNR-DT 212/2013 guidelines (CNR, 2013) according to the Italian building code commentary (MIT, 2019). This allowed the uncertainty modelling of geometric, as outlined in Table 1 where µ and s denote the mean value and logarithmic standard deviation (i.e. dispersion) of each random variable (RV), respectively. All RVs – except from the thickness of load-bearing walls ( t ) and tensile fracture energy of masonry ( G ft ) – were assumed to be lognormal. The equivalent frame modelling of URM buildings was based on the use of a fibre-based nonlinear macro element developed by Acconcia and Parisi (2020) , which performs a step-by-step integration of fibre response according to uniaxial constitutive models assigned to masonry in compression and tension. The nonlinear stress–strain equations proposed by Augenti and Parisi (2010) were adopted for masonry in compression, while assuming a linear elastic behaviour with exponential strain softening in tension according to previous studies (e.g., Parisi et al., 2016). The compressive behaviour was defined in accordance with peak compressive strength ( f m ), while setting the axial strain at peak strength to a value corresponding to the secant Young’s modulus ( E ) and assuming a deterministic