DYNAMIC MODELLING OF DISCRETELY SUPPORTED TRACK AND ROLLING NOISE ANALYSIS

Ballasted railway tracks consist of two rails discretely supported by sleepers located along the circulation direction. These sleepers serve to distribute the dynamic loads resulting from the wheel/rail interaction to the track foundation, which is typically composed of a layer of stones known as ballast. In contrast, slab tracks (also known as ballastless tracks) replace sleepers and ballast with a concrete slab, offering support for the rails, although these are generally less common than ballasted tracks. When comparing discretely and continuously supported configurations, differences in the dynamic behaviour of the rail become evident, such as the presence of the pinned‐pinned frequency characteristic of ballasted tracks due to the sleeper spacing. Various studies in the literature have shown that, despite these differences, the acoustic radiation of the track remains similar in both configurations. Moreover, it is widely acknowledged that sleeper spacing in practice is nonuniform, leading to spatially averaged vibrations (strongly correlated with the acoustic radiation) resembling those of continuously supported tracks. Consequently, it is common practice in the literature to employ continuous track models, distributing the properties of the rail foundation per unit length, for acoustic studies. In the work conducted, these hypotheses will be examined. Initially, the dynamic behaviour of a ballasted track will be compared with that of a continuously supported track, focusing on variables related to noise radiation, such as the track decay rate and the spatially averaged vibrations. Subsequently, the impact of sleeper spacing variability, modelled according to a Gaussian-like distribution, will be evaluated to assess assumptions commonly made in the literature.