In Greece, during the 1980’s, 60% of the twin-block concrete ties designed for 200 km/h, which were laid on a track with maximum operational speed of 140 km/h, presented serious cracks. The existing theories, in the French, German and American bibliographies, could not justify the appearance of these cracks since the calculated actions on the rail seat of the ties were much lower than the limit values of the regulations. This paper presents a model for the determination of the load acting on the rail seat of the ties in relation to the fluctuation of the substructure stiffness coefficient. The basic parameters influencing the estimation of the rail seat load — considering the most adverse conditions of a railway network — are investigated, and a methodology for calculating the load undertaken by each rail seat is presented. Numerical applications on twin-block and monoblock ties are presented, including the use of strain attenuating tie pads with high resilient fastenings. Finally, an application for the heavy-haul rail transport is presented, for the case of a track equipped with W24 fastening, Zw700WIC pad, rail 140RE type and concrete sleepers.

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