In modern High-Speed railways the necessity for achieving very low life13cycle costs has led to very well compacted -almost undeflected- substructure. Applications ofexcellent quality substructure are encountered in the French network with the operation of TGV(High-Speed Train in French) and also in research projects of the International Union of Rail16ways. The countervailing need for increased elasticity in the track's structure is satisfied withthe development of the very resilient fastenings with very soft pads. There is a long standingdiscussion about whether the very soft pads dispose a sufficient life-cycle for Heavy Haul rail19ways as well, as in the case of the US Railways. In this paper a parametric investigation througha theoretical approach is performed for the estimation of the actions on the track's support points(ties) with four methods from the international literature, both in High-Speed and Heavy Haullines, using values for parameters -mainly coefficients of stiffness- derived from measurementson track. Since the life-cycle of the pads and the clips of the fastenings is dependent on the ac24tions exerted on each tie per passing axle and the number of "axle-passes", this investigationleads to very significant ascertainments for the comparison of the actions on track in both cases.
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