PSI - Issue 78

Leandro Pancottini et al. / Procedia Structural Integrity 78 (2026) 1103–1110

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For each of the six models under examination, the maximum Interstory Drift Ratio (IDR) values were determined at the four corners, considering all two hundred accelerogram pairs. Figure 4 illustrates these results, with green markers indicating maximum IDRs in the X direction and grey markers for those in the Y direction. Non-converging analyses, indicated by empty markers, were excluded from the fragility curve generation.

Figure 4: NHA results in terms of maximum IDR in X and Y directions for the 6 structural models

The seismic analysis results reveal displacements, sometimes significant, in the Y direction, which is typically the most vulnerable. Inter-story drift ratios (IDRs) for BF models exceed those of IF models, owing to the significant contribution of infill walls to the overall structural stiffness. Numerous models showed non-convergences beyond IML 6 (return periods up to 1,000 years). 4. Fragility Curves Fragility curves were derived from the results of Multi-Stripe Analysis (MSA), using the IDR (Cornell et al., 2002; Ellingwood et al., 2007; Krawinkler and Lignos, 2009) as the global EDP (Terrenzi et al., 2022). Unlike other studies (Pancottini et al., 2025), a single EDP was employed in this context. Limit values for the different damage thresholds (Manfredi et al., 2023) were defined in accordance with the European Macroseismic Scale (EMS-98), providing a standardized reference framework for damage classification. Figure 5 shows the fragility curves for damage level D5. This level represents the most severe and irreversible damage, corresponding to an IDR greater than 2.5%. Damage of this magnitude seriously compromises the structural integrity of the building, highlighting the need for significant interventions.