PSI - Issue 64

Stefano Belliazzi et al. / Procedia Structural Integrity 64 (2024) 612–620 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The adopted capacity models are entirely based on the criteria provided by the current Italian standards NTC18 and the related commentary, with reference to Chapter 8, related to the analysis of existing buildings, consistent with the research objectives. The activation of the previously described local mechanisms is checked for masonry piers, while for the spandrels, only flexural and shear tension failures were analyzed according to commentary paragraph C8.7.1.3.1.1. For flexural verification, the capacity model (Lignola et al. 2008) involves the resistant moment M of the cross section of the structural element, assuming the conservation of plane sections and considering the stress-block model to describe the stress-strain relationship of the masonry in compression. In conclusion, for the verification of the masonry panels, the following formula was assumed: M p =(L 2 t σ 0 2 ) (1− σ 0 0.85 f m ) (1) where L is the overall length of the wall, t is the thickness, σ 0 is the average compression stress referred to the total area of the section, and f m is the average strength of masonry in compression. In the case of tensile axial load, the flexural capacity of the section is assumed equal to zero. For flexural analysis of the spandrels, the equation is: M = (0.4 f m h fs t) h fs 2 (1− 0.4 f m h fs t 0.85 f m h fs t ) (2) where h fs represents the height of the spandrel. For sliding shear and diagonal shear failures, the equations used in the analyses are evaluated respectively from the Mohr-Coulomb failure criterion (Labuz and Zang 2012) and the Turnsek-Cacovic formula (Turnšek and Cacovic 1971). The sliding shear capacity V s is: V s =L ′ t f v (3) where L' represents the length of the compressed part of the section assuming a linear compression diagram while f v is the shear strength depending on the average normal stress considering only the compressed part of the section under analysis. The shear tension capacity V t is: V t =L t 1.5 τ 0m p √1+ σ 0 1.5 τ 0m (4) Where τ 0m is the average shear strength and p is a corrective coefficient related to the stress distribution on the section depending on the slenderness of the wall. It can be assumed that p = h/L, defined between 1 and 1,5. 3. Structural models The structural models are generated by several Monte Carlo simulations (Belliazzi et al. 2021b) where the main input parameters are based on the National Group for Earthquake Defense (GNDT) database as shown in Table 1. In particular, the main parameters are provided in terms of geometric properties (interstorey heights h p ), mechanical properties of materials (specific weight γ M ) and gravitational loads (weight of generic floor W i and flat roof W c ). Each parameter depends on five different masonry substrates: poor-quality stone, good-quality stone, artificial bricks with a high percentage of voids, artificial bricks with a low percentage of voids and artificial masonry. It is important to note that interstorey heights and weight of floors are characterized by a normal probability distribution defined by a mean (μ) and a standard deviation (σ), while specific weights of different masonry substrates are defined by a constant value.