PSI - Issue 78

Emanuele Maiorana et al. / Procedia Structural Integrity 78 (2026) 57–64

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For all primary and secondary structural elements, as well as non-structural components and systems, it must be verified that the design demand (as specified in Table 7.3.III [7] for each required limit state) does not exceed the corresponding design capacity. Since the building is primarily intended for school use, it falls under Use Category III (§ 2.4.2 [7]), which accounts for significant crowding. This classification corresponds to a Usage Factor (CU) of 1.5 (Table 2.4.II [7]). The NTC2018 provides for class III buildings for school use (and class IV) the value of ﺡ E following the improvement interventions must in any case be no less than 0.6 (§ C8.4.2 [8]). Having defined the Nominal Life (Table 2. 4.I [7]), the subsoil category D (Table 3.2.II [7]), justified by the results of geological investigations carried out in recent years in areas bordering the site in question, and the topographic condition T1 (Table 3.2.III [7]), the data needed to determine the demand parameters to define the Elastic Response Spectra are obtained.

6. Numerical model

The wall thicknesses measured on-site were adjusted based on the values obtained during the verification campaign carried out by the testing laboratory. In some locations (Positions 2, 8, and 18), where the walls exhibited insufficient interlocking, a 2 cm gap (corresponding to the plaster thickness specified in the measurements) was introduced in the model. The structural analysis was performed using Strand7 (Finite Element Analysis System, Release 2.3.3). The numerical model was calibrated by comparing its results with simplified manual calculations to ensure accuracy. Fig. 11 illustrates the finite element model used for simulating seismic response.

Fig. 11. FEM numerical model consisting of 13402 nodes , 1375 beams , 10234 plates and 457 links .

Wall partitions with a thickness of less than 15 cm were excluded from the seismic-resistant system, and their structural contribution was neglected in the numerical model. Instead, their vertical loads were redistributed to adjacent elements, treating them as non-structural translational masses. In contrast, the floors were modeled as structural translational masses, partially distributed to the load-bearing walls. The numerical model was calibrated against flat-jack test results. The simulation produced stress values consistent with the experimental data.

7. Conclusions

Analyses of protected historical buildings, often serving social or strategic functions, reveal the need for seismic retrofitting interventions. These interventions should enhance the building's seismic performance by implementing sufficient modifications to improve safety while altering its global behavior. Given the structural complexity arising from centuries of modifications, material heterogeneity, and potential degradation, an extensive and costly testing campaign is essential. Such investigations provide data for developing accurate numerical models that reflect the building's true behavior, enabling the design of minimally invasive yet effective seismic upgrades. The number of tests directly influences the level of knowledge, the confidence factor, and ultimately the intervention strategy. If