PSI - Issue 78

Laura Giovanna Guidi et al. / Procedia Structural Integrity 78 (2026) 2154–2161

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developed in SAP2000. This dual verification approach allowed for a more robust assessment of the overall load bearing capacity and helped validate the consistency of numerical results, providing a broader overview of the static safety of the entire complex. The analysis highlighted a few localized elements that did not satisfy axial – bending (compression – bending) interaction checks at SLU. However, for each of these elements, the vertical load safety factor remains close to unity, indicating that even these local failure conditions occur only under minimal overload margins.

Fig. 7 Body 1 modelled by CDSWin: check at SLV in transversal direction The seismic vulnerability analysis was also conducted through independent single-unit modeling for each of the four blocks, using CDSwin software. As indicated by the previous evaluation of base shear distribution, Body 1, which accounts for approximately 45% of the total mass, is the most heavily stressed. The results described below therefore refer to Body1. A behaviour factor q = 1.5 was adopted, and the elastic response spectrum corresponding to a return period (T R ) of 712 years was applied, as required for the Life Safety Limit State (SLV). Under seismic action in the X direction, the structure exhibits a dominant first mode with a period T₁ = 3.93 seconds and a modal mass participation (M UX1) of 64%. Under seismic action in the Y direction, the third mode is dominant, with T₃ = 0.40 seconds (falling within the plateau of the response spectrum) and M UY3 = 45%. Based on these results, further analysis in CDSwin was carried out only in the transverse direction (i.e., the frame direction), which was deemed to be representative of the building's predominant seismic behavior. The linear modal dynamic analysis, performed in the Y direction (90°) for Body 1 revealed a generalized condition of non-compliance for the structure (red members in Fig. 7 ). In summary, considering that ξE is defined as the ratio between the resisting moment and the acting moment, and that the base shear in the frame direction of Body 1 amounts to 35% of its total weight, the following results were obtained: (i) no structur al element shows a ξE < 0.3; (ii) 45.6% of the elements exhibit a significant deficiency, with 0.3 ≤ξ E < 0.6; (iii) 44.1% of the elements present a moderate deficiency, with 0.6 ≤ξ E < 0.9; (iv) only 10.3% of the elements are compliant, with ξE > 0.9. The minimum ξE value from the analysis is 0.33, which is assumed as a global performance index for the structure.

Fig. 8 Check at SLV for Building : Axial force – bending moment interaction domain For Body 1, a detailed analysis was carried out using a three-dimensional model developed in SAP2000, aimed at evaluating the seismic response of the structural system under Life Safety Limit State (SLV) seismic loading conditions. For each geometric typology and floor level, the maximum values of bending moment (M) and axial force