PSI - Issue 78

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

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(Blocks 1, 2, 3, and 4) created using the CDSwin software, and global models of the entire complex (with and without infill wall cornices) implemented using SAP2000 (Fig. 3).

Fig. 3 Global and locals FE models by SAP2000 software

3.2. Dynamic characterization For the assessment of seismic vulnerability of the case study, a nonlinear static analysis has been done in compliance with N2 method (Fajfar, 1999; Fajfar, 2000). As previously described in the building overview, all units are constructed with unidirectional reinforced concrete frames oriented along the transverse direction. This structural configuration inevitably results in reduced stiffness and, consequently, increased vulnerability in the orthogonal direction. This weakness was clearly confirmed by the structural analysis results, which show higher natural vibration periods and more pronounced critical conditions specifically along that direction. The Fig. 4 derived from the SAP2000 model, illustrates the modal deformation corresponding to the first mode shape of Body 1 in the configuration without infill panels, revealing a distinctly flexural structural behaviour. The fundamental vibration period, approximately 6.69 seconds, confirms the significant longitudinal deformability. Table 1highlights the distribution of the effective modal mass along the principal directions , allowing identification of the main modes.

Considering the global models with and without infill panels (Fig. 5), the following observations can be made: along the X-axis, the cumulative participating mass significantly increases in the configuration with panels; it reaches approximately 80%, indicating a marked increase in longitudinal stiffness. This confirms that, although considered Fig. 4 First and second modal shapes of Body 1: comparison to evaluate the effect of infill panels