PSI - Issue 44

Giovanni Tondo et al. / Procedia Structural Integrity 44 (2023) 243–250 Giovanni Tondo et al. / Structural Integrity Procedia 00 (2022) 000–000

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2.2. The proposed Italian building portfolio

For each feature identified in the Da.D.O. platform, the corresponding incidence rate was evaluated to create a restricted set of buildings adequately representative of the entire database. This set consists of 100 buildings, whose geometrical and structural details were randomly assigned according to the identified statistical distributions for each feature. About 60% of the buildings were built before 1919 and only 2% after 2001 (Fig. 1a). The main structural detailing (i.e. the presence of perimetral beams) was defined based on the code provisions available in the selected construction period. Regarding the masonry quality, two categories are identified: good and bad; in Figure 1b it is noted that buildings with poor (i.e. bad) masonry are more common in percentage. The mechanical values for each typology are taken from the Italian building code (Circolare, 2019) assuming the average values in the proposed range. The “good masonry” is characterized by regular stone blocks in a good texture, while the “bad masonry” by irregular blocks in a disorganized texture.

(a)

(b) Fig. 1. Percentage of buildings per: (a) data of construction; (b) masonry quality.

Table 1 summarizes all masonry mechanical parameters, in which: f = average compressive strength; τ 0 = average shear strength without normal stresses (to be used in shear strength formula for irregular masonry); f v0 = average shear strength without normal stresses (to be used in shear strength formula for regular masonry); E = mean value of modulus of normal elasticity; G = average value of tangential modulus of elasticity; w = average specific weight. Table 1. Mechanical properties of bad and good masonry types, derived from the Italian Building Code (Circolare, 2019). Masonry quality Type of masonry f [N/mm 2 ] min-max τ 0 [N/mm 2 ] min-max fv 0 [N/mm 2 ] E [N/mm 2 ] min-max G [N/mm 2 ] min-max w [kN/m 3 ]

“Bad”

1,0 – 2,0

0,018 – 0,032

-

690 – 1050

230 – 350

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Irregular blocks in a disorganized texture Regular stone blocks in a good texture

“Good”

2,6 – 3,8

0,056 – 0,074

-

1500 – 1980

500 – 660

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Based on the observed data, the masonry buildings are generally characterized by a number of floors varying between one and four, an interstorey height between 2.50 and 3.5 meters, and in-plan dimensions lower than 230 m 2 . Following these considerations, the masonry building portfolio developed in this study is characterized by similar geometrical characteristics and assuming, for the random sampling, the percentage distributions reported in the Da.D.O. platform. Concerning the floor system, five categories are identified: beams with a deformable slab (wood beams with a thin wood slab); beams with rigid slab (concrete beams with concrete slab of 5 cm); beams with semi rigid slab (steel beams with brick vaults between them); vaults with chains; vaults without chains. In percentage they are all present almost uniformly, except for the system of vaults with chains, which is present only in 5% of the analysed buildings. Following this consideration, a consistent trend for the floor system was also considered in the proposed masonry building portfolio.