Track irregularities are deviations of the track from its design geometry and they are characterized by alignment, longitudinal level, cross level, twist, gauge. These parameters, that play an important role on the vehicle-track interaction phenomena, are periodically measured by the railway administrations, in order to monitor the evolution with respect to time of the track geometrical quality.

It is well known that track irregularities are an important source of vibration of coupled vehicle-track systems, influencing along with train speed, sleeper spacing, wheels creepage on curves, etc, the dynamic behavior of railways systems. Track quality is usually described by peak values of isolated defects and also by the standard deviation over a defined track length, typically 200 m. When characterizing track quality, three levels, given as a function of speed, are considered according to EN 13848-5 [1]: safety limit (SL), intervention limit (IL) and alert limit (AL).

In this paper, a study is presented for a better understanding of the vertical dynamic response of a coupled vehicle-track system to real track profiles. To fulfil this objective, two track segments of the Portuguese Railway Northern Line with different longitudinal profiles are considered in the numerical calculations. In general, random track profiles, defined for instance by power spectral density functions are used in the calculations due to the difficulty in having access to real track profiles. Some conclusions may be drawn with the present study. The dynamic force and the vertical track displacement increase with the reduction of track quality and decrease after maintenance operations are performed; the dynamic force is lower than the respective limit proposed in the Technical Specification for Interoperability for Infrastructure [2] if the standard deviation of the longitudinal level of the track is also inferior to the alert limit indicated in EN 13848-5 [1]. The results also show that an isolated defect induces, for the same traffic, higher dynamic forces and track displacements in comparison with the ones due to a distributed track irregularity, depending on its peak value. In short, track irregularities have an important role in vehicle-track interaction response which should be considered in future research in order to evaluate relationships between track quality, vehicle speed and dynamic forces on tracks.

1

EN13848-5 "Railway Applications - Track - Track geometry quality - Part 5: Geometric quality levels", CEN, 2008.

2

"ETI - Directiva 96/48/CE - Especificaçao técnica Interoperabilidade para o Subsistema "Infra-estrutura" do Sistema Ferroviário Transeuropeu de Alta Velocidade", Jornal Oficial das Comunidades Europeias, L 245, 12 Sept. 2002.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £145 +P&P)