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A new approach to the analysis and presentation of vertical track geometry quality and rail roughness
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2008 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 265, 1400-1496 p.Article in journal (Refereed) Published
Abstract [en]

A new approach on enhancing the assessment of track geometry quality and rail roughness by means of train–track interaction simulation and wavelength content analysis is presented. The dynamic model includes vehicle, track and linearized wheel–rail contact with moving irregularities and can be simulated either in the frequency domain by using FFT or in the time domain by constructing a filter function based on system identification technique. The system is suitable to calculate wheel–rail forces for very long track sections and for several vehicle types under a wide range of travelling speeds since the computational scheme is very efficient (300 km/s on a standard computer). With numerical results we demonstrate the potential benefits of improving conventional track geometry inspection methods and highlight short defects (0.5–2 m) as a cause of high dynamic wheel–rail interaction forces. By using a wavelength weighting of measured rail roughness a new improved way of analyzing rail roughness data is also presented. This improves condition assessment of tracks and rails and will enable the track engineer to monitor the track in a better way.

Place, publisher, year, edition, pages
2008. Vol. 265, 1400-1496 p.
Keyword [en]
Dynamic train–track interaction; Rail roughness; Track geometry quality
National Category
Vehicle Engineering
URN: urn:nbn:se:kth:diva-10353DOI: 10.1016/j.wear.2008.01.029ISI: 000258891700044OAI: diva2:216194
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-12-03Bibliographically approved
In thesis
1. Railway Track Stiffness: Dynamic Measurements and Evaluation for Efficient Maintenance
Open this publication in new window or tab >>Railway Track Stiffness: Dynamic Measurements and Evaluation for Efficient Maintenance
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Railway track stiffness (vertical track load divided by track deflection) is a basic parameter oftrack design which influences the bearing capacity, the dynamic behaviour of passing vehiclesand, in particular, track geometry quality and the life of track components. Track stiffness is abroad topic and in this thesis some aspects are treated comprehensively. In the introductionpart of the thesis, track stiffness and track stiffness measurements are put in their propercontext of track maintenance and condition assessment.

The first aspect is measurement of track stiffness. During the course of this project, Banverkethas developed a new device for measurement of dynamic track stiffness called RSMV(Rolling Stiffness Measurement Vehicle). The RSMV is capable of exciting the trackdynamically through two oscillating masses above one wheelset. The dynamic stiffness is acomplex-valued quantity where magnitude is the direct relation between applied load anddeflection (kN/mm) and phase is a measure of deflection-delay by comparison with force. Thephase has partial relationship with damping properties and ground vibration. The RSMVrepeatability is convincing and both overall measurements at higher speeds (up to 50 km/h)and detailed investigations (below 10 km/h) can be performed. The measurement systemdevelopment is described in Paper A and B.

The second aspect is evaluation of track stiffness measurements along the track from a trackengineering perspective. Actual values of stiffness as well as variations along the track areimportant, but cannot always answer maintenance and design related questions alone. InPaper D track stiffness is studied in combination with measurements of track geometryquality (longitudinal level) and ground penetrating radar (GPR). The different measurementsare complementary and a more reliable condition assessment is possible by the combinedanalysis. The relation between soft soils and dynamic track stiffness measurements is studiedin Paper C. Soft soils are easily found and quantified by stiffness measurements, in particularif the soft layer is in the upper part of the substructure. There are also possibilities to directlyrelate substructure properties to track stiffness measurements. Environmental vibrations areoften related to soft soils and partly covered in Paper C. One explanation of the excitationmechanism of train induced environmental vibrations is short waved irregular supportconditions. This is described in Paper E, where track stiffness was evinced to have normalvariations of 2 – 10 % between adjacent sleepers and variations up to 30 % were found. Anindicative way of finding irregular support conditions is by means of filtering longitudinallevel, which is also described in the paper. Train-track interaction simulation is used in PaperH to study track stiffness influence on track performance. Various parameters of trackperformance are considered, e.g. rail sectional moment, rail displacement, forces at wheel-railinterface and on sleepers, and vehicle accelerations. Determining optimal track stiffness froman engineering perspective is an important task as it impacts all listed parameters.

The third aspect, efficient maintenance, is only partially covered. As track stiffness relates toother condition data when studied from a maintenance perspective, vertical geometricaldefects (longitudinal level and corrugation/roughness) are studied in paper F. The generalmagnitude dependency of wavelength is revealed and ways of handling this in conditionassessment are proposed. Also a methodology for automated analysis of a large set ofcondition data is proposed in Paper G. A case study where dynamic track stiffness,longitudinal level and ground penetrating radar are considered manifests the importance oftrack stiffness measurements, particularly for soil/embankment related issues.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xii, 31 p.
Trita-AVE, ISSN 1651-7660 ; 2009:17
Railway track stiffness, maintenance, soil dynamics, measurement, simulation, vibration
National Category
Vehicle Engineering
urn:nbn:se:kth:diva-10360 (URN)
Public defence
2009-05-08, Sal D3, KTH, Lindstedtsvägen 5, Stockholm, 10:00 (English)
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-19Bibliographically approved

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