PSI - Issue 84

S. Lorefice et al. / Procedia Structural Integrity 84 (2026) 669 – 676

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consistent with the design drawings. Steel members were modelled using beam elements based on Timoshenko beam theory, while truss elements were employed for members intended to carry axial forces only. A 3D view of the implemented FEM model is shown below:

Fig. 6. 3D view of the FEM model

Permanent and variable actions were evaluated and applied to the model in accordance with the Italian Technical Standards (D.M. 17/01/2018) and the MdP-RFI. In particular, variable railway traffic loads were applied as line loads on the individual longitudinal girders through the definition of Traffic Line Lanes , along which the LM71 and SW/2 load models were applied. Both static and dynamic analyses were performed using finite element software. Static analyses accounted for the effects of permanent, variable, and traffic actions, considering different loading conditions and positions in order to maximize internal forces in all structural members. Linear dynamic analyses were carried out using the elastic response spectrum approach (behaviour factor q = 1.0). Modal properties were obtained using the Rayleigh–Ritz method, and modal combinations were performed using the Complete Quadratic Combination (CQC) rule, in accordance with §7.3.3.1 of the NTC 2018. 6 Results of Analyses and Checks – New Steel Deck The results of the numerical analyses were verified through comparison with simplified hand calculations performed according to the procedures outlined in §10.2 of D.M. 2018. Based on the outcomes of the numerical analyses, the structural verifications listed in Table 1 were carried out:

Table 1. Structural verifications performed Ultimate Limit State (ULS + SLV)

Resistance and stability checks in accordance with §4.2.3.2 and §4.2.3.3 of the NTC 2018, including bolted and welded connections. Checks according to the simplified coefficient method specified in §2.7.1.2 of the RFI Design Manual. Verification of horizontal and vertical deformations of the deck. Vibration: Passenger comfort assessment through control of vertical deflection of the deck and definition of maximum allowable limits according to train speed, span length, and truss structural system. Deformation:

Fatigue Limit State (FLS)

Serviceability Limit State (SLS)

Table 2 summarizes the maximum utilisation ratios derived from strength, stability, and fatigue verifications for each type of structural element. All values were found to be below unity, indicating satisfactory performance:

Table 2. Maximum Utilisation Ratios (Ed/Rd) max for Structural Elements STRUCTURAL ELEMENT ID (Ed/Rd) max

STRUCTURAL ELEMENT Longitudinal railway beams

ID

(Ed/Rd) max

Lower chords Upper chords

CI

0.899

LF 0.843

CS 0.928 M 0.994 TRF 0.971

Lower bracing Upper bracing Vertical bracing

CVI

0.347

Verticals

CVS 0.826 CVV 0.473

Railway crossbeams