Influence of Track Typology on the Dynamic Response of Short-Span High-Speed Railway Bridges

It is known that short-span high-speed railway viaducts are prone to suffer significant dynamic effects due to the passage of moving train loads. Recent technological advances in railway engineering have resulted in track typologies different from the conventional ballasted track consisting of discrete sleepers fastened to the rails and resting on a ballast bed. In particular, ballastless track has been identified as an effective solution due to reduced maintenance costs, high track stability and excellent geometric quality. Though different track typologies are available in the market, they can be classified as monolithic or independent according to the interaction degree with the bridge girder. In the present paper, the dynamic behaviour of short-span bridges is numerically studied by taking into account the track -bridge interaction by modelling explicitly the components of the track. Two types of ballastless track (monolithic continuous slab and independent short slabs) and conventional ballasted track are considered on simply supported bridges with span length in the range of 15-25 m subjected to envelope and commercial train loads at speeds between 200 and 360 km/h. In total, 2448 numerical cases have been analyzed. The study shows that dynamic deflections and accelerations produced at the bridge girder by moving train loads can be reduced when the ballasted track is replaced to ballastless track systems, especially for the critical speeds higher than 300 km/h. Moreover, it is shown that the two ballastless track systems lead to very similar results, with the monolithic system resulting in slightly smaller bridge deflections and also moderately larger accelerations.