PSI - Issue 78

Riccardo Maurizio Ambrogio Baltrocchi et al. / Procedia Structural Integrity 78 (2026) 9–16

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0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 Sa(T) [g] T [s] Type1 ξ = 2 % a vg = 1,0 g f.

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a.

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Fig. 1. Case study elements: (a) Ondal member; (b) I-shaped beam; (c) Vertical acceleration spectrum provided by Eurocode 8 for all soil types; Materials employed: (d) Advanced EC2 model for concrete C45/55; (e) EC2 bilinear elastic-hardening constitutive law for mild (B450C) and (f) EC2 bilinear elastic-hardening constitutive law for prestressing steel (Y1860). There are currently several roof element types, as well as prestressed beams. In this framework, the research focuses on the Ondal roof element spanning 25 m, widely used in structural design (Figure 1a). Furthermore, an I-shaped beam with 25 m span is designed and studied, to better explore their seismic behavior (Figure 1b). Subsequently, to investigate a possible dynamic interaction effect during seismic excitation, beams and roof elements are analyzed in coupled configuration. The coupled configuration consists of a central roof beam on which Ondal roof members rest on both sides with a 5 m spacing (interaxis). The elements considered were designed following classical static load combinations with environmental distributed loads typical of the Po plane, in Northern Italy. Non-structural loads considered include completing shells covering the free space between adjacent roof members, waterproofing layer and skylights. The I-shaped beam was designed considering the actual position of support of the roof elements with point loads. 2.2. Structural modelling Modelling and structural analyses are performed with the finite element code Straus7 (G+D Computing, 2010). The beams were modelled with non-linear beam elements to which the distributed plasticity was attributed through non-linear moment-curvature diagrams integrated by the software. Takeda hysteretic model is selected. To predict the non-linear flexural behavior of structural elements, sectional analysis for RC sections is performed. Non-linear moment-curvature diagrams can be modelled and analyzed, by solving the equations of equilibrium on the basis of advanced non-linear material modelling. The following materials are considered: • Concrete (C45/55) is modelled with the advanced EC2 model in compression, and with Sargin/Saenz model with non-linear softening beyond the peak strength in tension (Figure 1d). • Mild steel (B450C) is modelled using a bilinear elastic-hardening constitutive law following the recommendations of EC2 (Figure 1e). • Prestressing steel (Y1860) considers bilinear elastic-hardening constitutive law, as well as B450C mild steel (Figure 1f).