PSI - Issue 78

Federica Rauseo et al. / Procedia Structural Integrity 78 (2026) 473–480

478

The settlement profile is centred on the façade bay’s centroid in the X-direction, with a maximum vertical displacement of 0.10 m (Fig. 3); this 2D profile is then extruded along the Y- axis to generate a full‐plan 3D field. The resulting displacements are applied incrementally to the base nodes of the foundation springs with a load-controlled analysis, after which the pushover is carried out under displacement control with a uniform lateral load distribution. In the notation used throughout the analysis, configurations including settlement effects are denoted by suffix ‘S’ (e.g., AB–S, CA–S, CB–S), indicating that the settlement profile was applied prior to the pushover phase. Since the building is symmetric with respect to the Y-axis, the structural response to pushover in the X-direction is independent of the sign. Conversely, due to asymmetry along the X-axis, pushover analyses in the Y-direction were performed in the positive direction +Y. Accordingly, all results and figures related to the Y-direction refer to this positive loading case. 5. Results and discussion The discussion focuses on the influence of corrosion and differential settlements on the elastic and inelastic response of the building, as captured through modal analysis and pushover simulations. Table 1 summarises the natural periods of the building for the first three modes for both Model A and Model B, across the different configurations. The first mode is primarily associated with translation along the X direction, the second mode with translation along the Y-direction, while the third mode exhibits a predominantly torsional behaviour. Overall, the modal shapes are consistent across all cases. A general observation is that corrosion has a negligible effect on the global elastic stiffness: the periods remain substantially unchanged between the as-built and the corroded configurations. This is coherent with the fact that the damage is localised at the base and affects only a limited number of elements, without significantly altering the global stiffness. When comparing the two modelling strategies, Model B consistently shows longer periods than Model A across all configurations. This systematic increase - ranging from about 10 % to 14 % for the first two modes - can be attributed to the explicit modelling of continuous foundation beams i n Model B because these structural components introduce additional masses to the structure. Fig 4. (a) shows the pushover curves in terms of base shear vs control displacement, for both directions in their as built configuration. Due to the structural layout, the base shear capacity is significantly higher in the Y direction (parallel to the RC frames) compared to the X-direction. The two models show overall good agreement in terms of initial stiffness and strength, especially up to peak; more noticeable differences emerge in the post-peak range. Given the structural relevance of the Y-direction, for the sake of brevity the following discussion focuses on this case thus, suffix ‘PY’ is omitted when referring to the different case studies. Fig. 4 (b) shows the effects of corrosion on the capacity curves in the Y-direction. For both models, the CA configuration shows the greatest deviation from the as- built response, particularly in Model A, where a pronounced strength drop and reduced displacement capacity are more evident. Conversely, the CB case remains closer to the original curve, especially in Model B. These trends highlight the effect of corrosion when considered alone: in the absence of settlements, uniform corrosion at the base of all columns leads to a more significant reduction in lateral strength than corrosion concentrated at the façade, which involves a smaller number of structural elements. This behaviour is reflected in the base shear reductions reported in Table 2, where the notation X–Y indicates the percentage reduction in peak base shear of configuration Y compared to configuration X. When differential settlements are implemented, the role of corrosion becomes more critical. The presence of settlements aggravates the consequences of pre-existing damage: both CA and CB configurations show additional reductions in lateral capacity when combined with soil-induced displacements. This is particularly evident in the CBS case, where façade columns are corroded along their entire height. In this condition, localised damage due to corrosion, Table 1. Periods of the first three modes of vibration. Model A Model B AB CA CB AB CA CB T 1 [s] T 2 [s] T 3 [s] 0.89 0.71 0.66 0.91 0.73 0.68 0.90 0.72 0.67 0.99 0.8 3 0.67 1.01 0.84 0.68 1.01 0.83 0.6 8