PSI - Issue 78

Giada Frappa et al. / Procedia Structural Integrity 78 (2026) 17–24

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The building is covered by a double-pitched roof composed of light steel profiles directly supported by the main beams and perimeter columns of the top floor. Staircases are composed of cast-in-place sloped RC slabs, located, together with the elevator core, within the penultimate structural bay at the northeast corner of the building (Fig. 1b). This configuration introduces plan eccentricities between the center of mass (CM) and center of rigidity (CR) of 2.32 m along the X axis and 4.77 m along the Y axis. The RC slabs of the stair flights and landings are 160 mm and 180 mm thick, respectively. The Y-direction structural walls are made of full-height precast RC panels, each corresponding in length to one structural bay, and having a thickness of 120 mm. The structural system is completed by non-load-bearing precast façade elements, either blind or windowed, which rest continuously on the edge beams or perimeter columns and are mechanically anchored to them. 3. Analysis and verification of the as-built configuration 3.1. Actions definition The values of dead structural loads and dead non-structural loads were derived from the information provided in the available design reports and drawings. The live loads and their combination factors were determined in accordance with the provisions of the Italian Building Code (NTC 2018). Regarding the seismic action, six artificial horizontal spectrum-compatible accelerograms were generated using the software SIMQKE_GR by Piero Gelfi, in accordance with the seismological, stratigraphic, and topographic characteristics of the construction site. These accelerograms were used to define three time-history records, each consisting of a pair of independent accelerograms combined in accordance with the provisions of NTC 2018. The structural response was evaluated by means of a Fast Nonlinear dynamic Analysis (FNA, Wilson, 2002) considering the most unfavorable values of the resulting internal forces. 3.2. Material strengths With regard to the material strengths adopted for the verifications, the information obtained from the original design documents, along with the results of both destructive and non-destructive investigations carried out on the structure, have allowed the attainment of knowledge level LC2 in accordance with Commentary on NTC 2018 (2019). This level corresponds to a Confidence Factor CF = 1.20. The design strength values differ according to the collapse mechanism, ductile or brittle, and are reported in Table 1, where and are the concrete average compression strength and the steel average yield strength, respectively, and are the corresponding design values, and and are the safety factors. Table 1. Design strength values of the materials.

Mechanism type Steel Ductile mechanism = = 317,2,4 = 31,2 = = 414,32,5 = 369,6 Brittle mechanism = ∙ = 1,327∙,14,5 = 20,8 = ∙ = 1,424∙31,,515 = 321,4 Concrete

3.3. Finite element model

The finite element model of the building was developed using SAP2000 software by Computers and Structures Inc. (Version 25.1.0). Frame elements were employed to model beams and columns. To simulate the effects of prestressing in the main beams, Tendon objects were used. Considering the assembly procedure of the precast elements, the beam-to-column connection was modeled as a hinge , while the column-to-foundation connection was