Sensitivity Analysis of Fastenings’ Types on Track's Life-Cycle

During the study for the dimensioning as well as the selection of the individual materials constituting a railway track, the ballast and the substructure present residual deformations, directly related to the deterioration of the geometry of the track. The slighter the residual deformations and the slower their alteration over time is, the better the quality of the track. The actions acting on the track panel are almost proportionally dependent on the total track stiffness that is also influenced seriously by the fastening’s and total track’s stiffness. This implies that the average stress on ballast underneath the sleepers’ seating surface is also influenced by the stiffness. It is imperative to reduce as much as possible the average stresses at the sleepers’ seating surface, by increasing track’s stiffness. In the Greek network since the late 1980’s up to 2000 an extended research program was performed due to cracks on twin-block concrete sleepers (over 60% on the total number laid on track). In the frame of this investigation, a new approach for the actions on sleepers and the ballast has been developed, by taking into account the real conditions of the line (maintenance etc.) which led to the increase of the demands in the specifications for the use of very resilient fastenings. In this paper a Sensitivity Analysis is attempted for different types of fastenings: rigid and resilient.