PSI - Issue 78

Marina Serpe et al. / Procedia Structural Integrity 78 (2026) 1000–1007

1003

3. Phase 1: Definition of Case Studies The first step of the study involved defining a reference façade (Fig. 2a) representative of typical unreinforced masonry buildings. The geometry of the façade consists of two storeys and three piers, with a total height and width of 6435 mm and 6000 mm, respectively and a constant thickness of 250 mm (Magenes Guido, R, and Calvi Gian Michele 1995). Starting from this reference configuration, in the second step (Fig. 2b), a series of models was generated by varying the in-plane dimensions of the structural elements, specifically the piers and spandrels. These variations were introduced by modifying the wall's opening ratio, which ranged between 10% and 30%, to ensure realistic values consistent with those commonly observed in existing buildings. In addition to the variation in opening percentage, the analyses were carried out considering, for each model, two different assumptions for the floor slab behaviour: one assuming a flexible floor and the other a rigid floor. Finally, in the third step, variations in settlement conditions were introduced into all previously generated façade models. The parametric study explored three main aspects: the magnitude of vertical downward displacement, which was progressively increased from 0 mm to a maximum of 30 mm; the position where settlement was applied, considering either the centre or the edges of the wall base; and the extension of the affected area in terms of the number of piers involved. In the case of central settlement, only the central pier was subjected to displacement, while for lateral settlement scenarios, either one or both lateral piers were affected, thereby simulating localized or more distributed settlement patterns. These configurations led to the definition of three distinct settlement profiles, central, one-pier lateral, and two-pier lateral, depending on the combination of position and extent of the applied displacement (Fig. 2c). Considering the asymmetry of the problem due to boundary conditions (e.g., lateral settlement profile) or the arrangement of openings, pushover analyses were carried out in both directions of the in-plane façade axis. This was achieved by applying the horizontal load in both the positive and negative directions of the x-axis, introducing an additional parameter in the study.

Phase 1: Definition of Case Studies

Floor stiffness

a

b

Opening ratio

Two-piers lateral settlement

One-pier lateral settlement

Central settlement

c

Fig. 2. Parametric definition of the case studies: (a) Reference geometry (measures in mm); (b) Geometrical and structural variations and (c) Settlement profiles variation. 4. Phase 2: Numerical Modelling and Pushover Analyses The nonlinear static analyses were performed using the finite element software Abaqus. The masonry walls were modelled with 2D shell elements ( CPS6M ). The Concrete Damaged Plasticity (CDP) material model, available in the software, was adopted and calibrated using experimental data from the literature (Magenes Guido, R, and Calvi Gian Michele 1995). summarizes the parameters used for the calibration of the CDP material model; while Fig. 3 shows the adopted compression (Fig. 3a) and tension (Fig. 3b) bilinear stress–strain relationships introduced. The wall was firstly subjected to self-weight and a uniformly distributed load (10 KN/m 2 per floor) at the floor levels. The settlement was applied introducing a movable rigid block at the wall base and subjected to vertical displacements under quasi