PSI - Issue 64

Annalisa Mele et al. / Procedia Structural Integrity 64 (2024) 1295–1302 A. Mele et al./ Structural Integrity Procedia 00 (2023) 000 – 000

1298

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(East-West) and vertical directions are modeled as settlements imposed at the base of the first floor piers. Finally, the damage evolution in the infills is studied, by fixing different DSs according to literature thresholds (Section 3.2). 3.1. Structural features and modeling The elements sizes have been defined through visual inspections, and a simulated design of the building has been carried out to define all the structural details, according to the Italian Ministerial Decree, D.M. LL.PP. (1974). In Table 1 the geometrical features of columns and beams are reported in terms of section dimensions, number and diameters ( Ø ) of the longitudinal ribbed steel bars, and diameters ( Ø ) and span/lengths of the stirrups. The mechanical properties of the materials have been estimated based on code references (for concrete, Italian National Standard NTC 2018), literature indications (for tuff bricks, Commentary to the Italian National Standard NTC (2018); for hollow clay bricks, Ricci et al., (2018), and Di Domenico et al., 2019) and validated tools (for steel, Reluis software STIL). The values of the main features are reported in Table 2 and Table 3.

Table 1. Geometrical features of columns and beams Section [cm]

Longitudinal bars [Ø in mm]

Stirrups [Ø in mm]

Columns

40×40

n.4× Ø 18

Ø 8/25 cm

30×60 (floor 1 and 2)

Ø 8/20 cm (floor 1 and 2)

n.4× Ø 18 (compression) n.2× Ø 18 (tension)

Beams

35×60 (rooftop)

Ø 8/15 cm (rooftop)

Yield strength [ ⁄ ] Compressive strength R ck [ ⁄ ] Elastic modulus [ ⁄ ] - 25,00 30.200 Elastic modulus [ ⁄ ] Shear modulus [ ⁄ ] Tensile strength [ ⁄ ] 1410 450 0,06 473,90 - 200.000

Table 2. Concrete and steel - mechanical properties

Concrete C20/25

Steel B450C

Table 3. Infills - mechanical properties

Tuff bricks

Hollow clay bricks

1255

315

0,22

The finite element model is composed by mono-dimensional elements for beams, columns, and infills. In particular, the infills are modeled with equivalent diagonal struts compression-resisting, following the previsions of Fardis (2009). The first floor piers are constrained at the base to simulate the presence of the foundations. An image of the finite element model is shown in Figure 3a. The ductile behavior of the RC elements is assigned as concentrated plastic hinges, located at the end of the mono-dimensional elements, for beams and columns. The shape of the plasticity model assigned to beams and columns is shown in Figure 3b. As regards the infills, the lateral force displacement response is modeled according to the equivalent single strut model formulated in Panagiotakos and Fardis (1996), schematically shown in Figure 3c, and it is assigned in the middle of the structure. The structural model has been validated by evaluating the total lateral response of the building by performing pushover analyses. The results of these analyses, as well as all the details about the abovementioned backbones, can be found in Miano et al. (2021).

(a) (c) Fig. 3. (a) Finite element model of the case study building; scheme of (b) plastic hinges backbones of RC beams and columns, and (c) lateral force-displacement behavior for infills by Panagiotakos and Fardis (1996). (b)