PSI - Issue 75

Elena Sidorov et al. / Procedia Structural Integrity 75 (2025) 276–288 Elena Sidorov et al. / Structural Integrity Procedia (2025)

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2. State of the Art 2.1. Design recommendations of new Eurocode generation

Currently, the European design standard EN 1993-6 (2005) for crane supporting structures is under revision. The revised version to be released as prEN 1993-6 (2024) will contain a new design recommendation to verify intermittent rail welds against fatigue, compare Clause 7.8.2(7) of prEN 1993-6 (2024). The maximum value of the local vertical compressive stress σ nom , that is generated in chain intermittent rail welds (double fillet welds) due to a single wheel load F , may be determined by Eq. (1), where p is the maximum vertical force in both welds per unit length as shown in Figure 2, that is referred to as ‘weld pressure’ in this paper, and a is the size of the single rail weld. (1) For chain intermittent rail welds as shown in Figure 1d, the maximum weld pressure p is calculated according to Eq. (2) where b r and h r are the nominal cross-sectional dimensions of the crane rail. nom / (2 ) = p a σ

F F

p

= =

(2)

+ b h



eff

r

r

Up to now, prEN 1993-6 (2024) has limited the application of Equation (2) to chain intermittent rail welds with a length of ℓ w = 50 mm. This nominal stress definition corresponds with a detail category 40 ( ∆ σ C = 40 N/mm²) as shown in Figure 3. Design recommendation to calculate the weld pressure of staggered intermittent welds are currently not available. The influence of transverse stiffeners on the weld pressure has not been known up to now.

Fig. 2. Weld pressure of chain intermittent rail welds

2.2. Background of the new fatigue design recommendation for chain intermittent rail welds The fatigue verification of intermittent rail welds, that is proposed by prEN 1993-6 (2024), was developed by Kuhlmann et al. (2022). The proposed nominal stress formula, compare Equations (1) and (2), was formulated in connection with fatigue tests on large-scale girders exposed to a travelling wheel load. Based on engineering judgement, the nominal stress formula assumes technical contact between the rail and the top flange of the crane runway beam. Unavoidable surface irregularities of the contact surface between the crane rail and the top flange, that were frequently observed in practice and that might exceed the extent the irregularities of the tested girders, were not taken into account explicitly. It furthermore was assumed in the nominal stress formula that composite top chord, comprising the crane runway’s top flange and the crane rail, is only supported by the web of the crane runway beam. The influence of transverse stiffeners that might have an influence on the stiffness of the top chord and eventually affect the weld pressure is neglected.