PSI - Issue 84

Gian Felice Giaccu et al. / Procedia Structural Integrity 84 (2026) 991–998

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stress and integral ratios than the rigid connection case, reflecting diminished composite action due to interface slip (Silva & Dias 2018; Feng et al. 2020). 2.2. Non-linear analysis A comprehensive parametric study was performed by varying key mechanical properties of the composite system, which are known to govern structural performance at the onset of plastic behavior. To streamline the analysis and enable generalization across different deck configurations, a mechanical deck ratio was introduced. This non-dimensional parameter characterizes the relative stiffness and strength contributions of the steel and concrete components within the composite section, offering a unified framework for interpreting the nonlinear response. Bilinear constitutive laws were used in accordance with Eurocode 4:2004 for composite behavior, with steel properties defined following Eurocode 3 (Annex C, §C.6, EN 1993-1-5:2006). Concrete was modeled based on Eurocode 2, using the uniaxial constitutive relationships for monotonic loading conditions as specified in Table 3.1 (EN 1992-1-1:2004), consistent with formulations adopted by Tasnimi and Lavasani (2011). A total of six representative cross-sections were selected for detailed analysis, each located at different longitudinal positions along the deck corresponding to non-dimensional coordinates  = 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2. For each cross-section, the axial force was progressively increased over 50 incremental load steps until the plastic resistance N pl,Rd of the section was reached. The reference values for N pl,Rd were computed in accordance with Eurocode 4:2004 and are summarized in Table 1, which outlines the material and geometric properties of all composite deck configurations considered. Further comparisons between linear and nonlinear behavior are shown in Figs. 4 and 5, focusing on the cross section at  = 0.2 under two discrete load levels: 50% and 100% of N pl,Rd .

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Fig. 4. T1 Case. Linear and non-linear parametric study for all the cross-sections, with  = 0.06, for the 50% of N pl,Rd , (a) stress ratio Σ and (b) normalized force as a function of χ for = 0.2.

Fig. 5. T1 Case. Linear and non-linear parametric study for all the cross-sections, with  = 0.06, for the 100% of N pl,Rd , (a) stress ratio Σ and (b) normalized force as a function of χ for = 0.2.

These cases, as outlined in Table 1, provide a representative view of the system’s nonlinear response near the load introduction point. For brevity, intermediate load cases at 25% and 75% of N pl,Rd are not presented but follow the same