PSI - Issue 78

Mariano Di Domenico et al. / Procedia Structural Integrity 78 (2026) 1237–1244

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buildings share the same regular structural plan and similar storey heights (Fig. 1). The RC structures reflect the detailing and materials of each period: plain rebars and lower concrete strength for 1950s buildings, and deformed bars with improved concrete strength for later decades (Verderame et al. 2001; Verderame et al. 2012). The seismic load distribution also evolved from uniform (1950s) to linear (later decades).

3P50 and 3P70

3P90

6P50 and 6P70

6P90

Fig. 1. 3D sketch of the case-study structures.

Infills are double-leaf masonry walls with horizontally perforated bricks and low-quality mortar. Mechanical properties are the same for all buildings, reflecting non-structural lightweight masonry (Liberatore et al., 2018). The external leaf thickness varies by construction period, from 12 cm to 15 cm, to reflect changes in insulation standards. Openings are present on the long sides, with an average opening ratio of 30%. Staircases were designed only for gravity loads. Full details are provided in De Risi et al. (2023) and Di Domenico et al. (2023). The buildings were modelled nonlinearly in OpenSees (McKenna et al., 2010) using a lumped plasticity approach (Barbagallo et al., 2023). Beams and columns were assigned empirical quadri-linear moment – rotation curves, with plastic hinges at member ends. Moment capacities and chord rotations were based on Di Domenico et al. (2021) for plain bars and Haselton et al. (2008) for ribbed bars. Shear failure and axial failure in columns were modelled following Aslani and Miranda (2005). Beam-column joints were included using the scissors model (Alath and Kunnath, 1995), with parameters from De Risi et al. (2017), Celik and Ellingwood (2008), and Jeon et al. (2015). Masses were lumped at each floor level. The in-plane infill behaviour was modelled with an equivalent strut approach, considering elastic stiffness, strength, and drift limits (Decanini and Fantin, 1986; Cardone and Perrone, 2015; Sassun et al., 2016; Liberatore et al., 2018). Correction factors for openings were included (Decanini et al., 2014). The out-of-plane infill behaviour, central to this study, was modelled using the strategy by Ricci et al. (2018a). A trilinear force – displacement envelope was assigned through ZeroLength elements, with interaction between in- and out-of-plane damage included via conditional activation/deactivation rules. Collapse displacement was defined as 0.80 times the thickness of the wall leaf (Angel et al., 1994). Strength reductions due to openings were modelled following Mays et al. (1998), and degradation due to in-plane drift or out-of-plane displacement followed Ricci et al. (2018a; 2018b; 2022). Full modelling details are available in De Risi et al. (2023) and Di Domenico et al. (2023).