PSI - Issue 78

Roberta Di Chicco et al. / Procedia Structural Integrity 78 (2026) 497–504

501

3. Numerical analyses on a prototype aggregate 3.1. General features and structural modelling

Defining the taxonomy of masonry aggregates based on geometrical aspects, such as planimetric layouts and the in-plan arrangement of resisting elements, and typological-structural features, like masonry and floor types, is a critical and preliminary step for the development of vulnerability models using both macroseismic and numerical methods (Ruggieri et al. 2023, Di Chicco et al, 2025). For this reason, in this study a prototype aggregate according to the above illustrated exposure analysis was defined and it is shown in Figure 4. The aggregate exhibits a rectangular layout, with a gradual reduction in transverse width and a longitudinal length of 43 meters. In addition to this plan irregularity, elevation irregularities are also present, as the number of storeys varies between one and three. It consists of multiple mutually connected structural units and is located on a flat lot. For the most part, it rises two storeys above ground, with a maximum eaves height of nine meters, and features pitched roofs. The structural model of the aggregate was developed using the 3Muri software (S.T.A. DATA srl), where the walls are modelled as interconnected macroelements of three different types (piers, spandrels and rigid nodes).

a)

b)

Fig. 4. (a) Three - dimensional model and (b) Macroelement model of the aggregate under study, developed using the 3Muri software.

Depending on the masonry type, wall thicknesses range between 40 and 80 cm. The horizontal structures are mostly composed of floors made of steel beams (IPE 140 in S235 steel) with a spacing of 80 cm and a 4 cm concrete topping slab. The roof structures are also made of steel. A knowledge level of LC1 was assumed for the buildings under investigation, corresponding to a confidence factor (FC) of 1.35. The mechanical properties of masonry are reported in Table 1.

Table 1. Mechanical properties.

Masonry type

f m [N/cm

2 ]

τ [N/cm 2 ]

E [MPa]

G [MPa]

W [kN/m 3 ]

Irregular (rough stones) Regular (tuff stones)

100 200

1.8

870

290 450

19

4 16 Note: f m : compressive strength; τ: shear strength, E: Young Module; G: Shear Module; W: density 1410

The 3D macroelement model (Figure 4b) is then converted into an “equivalent frame model” for performing nonlinear static analyses. The resistance criteria for piers and spandrels are defined according to the provisions of EN 1998-3, where the allowable drift limits are 0.4% for shear failure and 0.6% for flexural collapse. Analyses were carried out in the two main structural directions, X and Y, considering two lateral load distributions (static forces and uniform), according to the provisions, NTC2018. A total of 24 pushover analyses were performed. In all the examined cases, the analyses were stopped at a 20% reduction of the maximum base shear capacity. Numerical checks were carried out assuming soil category “B” and using an elastic design spectrum corresponding to the Life Safety Limit State (SLV) for the specific site, following the N2 method. The control node for all the analyses is