PSI - Issue 81

Roman Samchuk et al. / Procedia Structural Integrity 81 (2026) 184–191

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3.3. Sensitivity to drive dynamics

The baseline horizontal-action e ff ect is obtained for φ 5 = 1 . 5. This is a variable parameter which, in this analysis, is selected under the assumption that existing backlash does not significantly influence the dynamic forces (e.g. as is typical for gearboxes), resulting in a smooth change of forces. However, in cases of sudden force changes, this parameter may increase up to 2, which corresponds to a 33% increase relative to the value of 1.5. For drives with considerable backlash (such as open gear systems), φ 5 can reach values up to 3, e ff ectively doubling the dynamic factor and worsening the fatigue results.

4. Conclusions

• The statement that horizontal crane actions are normally negligible for fatigue should not be interpreted as a default exclusion rule; typical operational scenarios can include frequent cyclic horizontal actions that a ff ect stress ranges at fatigue-critical details. • In the researched case study, including horizontal actions increased the governing fatigue damage by about 22%, which can change verification outcomes depending on the detail category and weld assumption. • The influence of horizontal actions is sensitive to drive dynamics; backlash and abrupt force changes can further increase the horizontal-action contribution beyond the baseline considered here. • For practical verification, horizontal actions should be explicitly considered whenever vertical-only utilization is close to allowable or when operational conditions indicate frequent acceleration / braking events • The current evaluation is based on a rigid rail-to-girder load transfer and a welded web–flange connection. Therefore, alternative rail attachment systems and web–flange joint configurations should be analysed addition ally to validate the broader applicability of the conclusions (e.g., clamped rail connections with an elastomeric pad, non-welded or hybrid web–flange connections).

Appendix A. Mesh convergence study

Fig. A.4. Mesh convergence study: stress level at the critical web–flange location depending on the number of elements in the local web area under the wheel load.

A local mesh convergence check was carried out for the critical web–flange region under the governing wheel load. Seven mesh configurations (A–G) were analysed with a progressively refined element size in the local web area beneath the rail, while the global model, loading and boundary conditions were kept unchanged. Figure A.4 shows the stress level at the critical point as a function of the number of shell elements in this region. From the coarsest