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Measurements of track stiffness and track irregularities todetect short waved support conditions
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2006 (English)In: International Conference on Railway Track Foundatons, 2006Conference paper, Published paper (Refereed)
Abstract [en]

Short waved vertical irregularities of the track can cause high dynamic train-track interactionforces. These forces cause several problems, for example deterioration of track geometry anddamage of components. Since these short irregularities also could be an important source ofpropagating waves and environmental vibration, different measurement and evaluation techniques have been investigated to detect and quantify these irregularities. The RMSV(Rolling Stiffness Measurement Vehicle) developed by Banverket has been used to verify thephenomenon of track stiffness variability. Variations of 5 – 20 kN/mm (2 – 10 %) betweenadjacent sleepers are common, and variations even up to 60 kN/mm (30%) have been detectedon a modern ballasted track. Also a new way of analysing longitudinal level, measured with atrack recording car (TRC), by filtering out only short waved irregularities makes it possible toindicate problems with hanging sleepers, variable sleeper support and other possible shortwaved irregularities. Even though the amplitude of these irregularities is low (around 0.5 – 1mm), their impact can be considerable.

Place, publisher, year, edition, pages
2006.
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10352OAI: oai:DiVA.org:kth-10352DiVA: diva2:216192
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-20Bibliographically 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.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:17
Keyword
Railway track stiffness, maintenance, soil dynamics, measurement, simulation, vibration
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10360 (URN)
Public defence
2009-05-08, Sal D3, KTH, Lindstedtsvägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-19Bibliographically approved

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