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Railway Track Stiffness: Dynamic Measurements and Evaluation for Efficient Maintenance
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
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 [en]
Railway track stiffness, maintenance, soil dynamics, measurement, simulation, vibration
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10360OAI: oai:DiVA.org:kth-10360DiVA: diva2:216214
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
List of papers
1. Continuous Track Stiffness Measurement: An Effective Method To Investigate The Structural Conditions Of The Track
Open this publication in new window or tab >>Continuous Track Stiffness Measurement: An Effective Method To Investigate The Structural Conditions Of The Track
2002 (English)In: Railway Engineering Conference, 2002Conference paper, Published paper (Refereed)
Abstract [en]

Vertical track stiffness and its variations along the track are important parameters that affect the conditionof the track, in particular the deterioration of track geometry and ballast degradation. The track stiffness isalso an important factor that has to be considered when upgrading the track for traffic of higher axle loads and higher speeds. Within the EU project EUROBALT II, Banverket (Swedish National Rail Administration) has developed a method to continuously measure the vertical track stiffness. Recently,Banverket has made further improvement of the method and carried out extensive measurements in Sweden using our track-loading test vehicle. Different combinations of excitation frequency and speedhave been tested. The measurement results have shown a significant correlation with actual geotechnical conditions and depth of soil layers. The measurement method has also shown very good repeatability. In this paper, we introduce the method of continuous track stiffness measurement and report the promising results we have obtained. It can be concluded that the continuous track stiffness measurement provides an effective way to investigate the structural condition of the track and should be a very useful tool for determining the cause of certain track problems.

National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10346 (URN)
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-11-23Bibliographically approved
2. Simulation, Development and Field Testing of a Track StiffnessMeasurement Vehicle
Open this publication in new window or tab >>Simulation, Development and Field Testing of a Track StiffnessMeasurement Vehicle
2005 (English)In: 8th Interntaional Heavy Haul Conference, Rio de Janeiro, 2005Conference paper, Published paper (Refereed)
Abstract [en]

A new vehicle for continuous measurement of vertical track stiffness has been built by Banverket. Two oscillatingmasses of the vehicle excite the track dynamically and the track stiffness is calculated from measured axle box forces andaccelerations. The stiffness is given as a complex quantity and presents both the magnitude and the phase. The repeatability isvery good, and some promising results for soft subsoils are shown. Both overall measurements at higher speeds (up to 60km/h) and detailed investigations (below 10 km/h) can be performed.

Keyword
Track stiffness, Simulation, Measurement, Track maintenance
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10347 (URN)0-646-33463-8 (ISBN)
Conference
14th-16th of June 2005, Rio de Janeiro
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-11-23Bibliographically approved
3. Identification of Substructure Properties of Railway Tracks by Dynamic Stiffness Measurements and Simulations
Open this publication in new window or tab >>Identification of Substructure Properties of Railway Tracks by Dynamic Stiffness Measurements and Simulations
2010 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 329, no 19, 3999-4016 p.Article in journal (Refereed) Published
Abstract [en]

A new vehicle has been developed to measure dynamic vertical track stiffness while in motion. This technique allows the resonance behaviour of the track below 50 Hz to be measured. Soft soils like clay and peat are the main causes of resonance below 20 Hz. By means of simulation studies with the software VibTrain, soft soil resonance behaviour may be characterized using a few key parameters originating from track stiffness measurements, such as the minimum phase delay and corresponding frequency of the receptance transfer function. Statistical models are built to relate these key parameters with substructure properties, such as embankment thickness, shear wave velocity and thickness of the soft soil layer using pattern recognition methods. Two case studies are used to show the methodology, and the results are verified using Ground Penetration Radar (GPR) measurements and borehole investigations. Models are also developed from the statistical relationship between GPR-data and stiffness measurements. It is shown that embankment thickness is the easiest quantity to estimate, but indicative results are also presented for the other quantities (shear wave velocity and thickness of soil layer).

 

Keyword
vibration, trains, speed
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10350 (URN)10.1016/j.jsv.2010.04.015 (DOI)000279062200010 ()
Note
Uppdaterad från submitted till published(20101123) QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2017-12-13Bibliographically approved
4. Monitoring and Substructure Condition Assessment of Existing Railway Linesfor Upgrading to Higher Axle Loads and Speeds
Open this publication in new window or tab >>Monitoring and Substructure Condition Assessment of Existing Railway Linesfor Upgrading to Higher Axle Loads and Speeds
2006 (English)In: 7th World Congress on Railway Research, 2006Conference paper, Published paper (Refereed)
Abstract [en]

Many of the European railways have been designed for completely different traffic conditions than thoserequired today. Upgrading of existing railway lines for higher axle loads and speeds requires new modernmethods for in situ investigation of the railway ballast and substructure. Combination of continuousmeasurements of track geometry quality and non-destructive methods like dynamic track stiffness and Ground Penetrating Radar (GPR) can be a good example of obtaining the important information about theconditions of existing railways. A new methodology for evaluation of all available measurementscompleted with results from geotechnical investigations is proposed to study problems dealing with railway structure and subgrade in case upgrading or maintenance work is required.

Railway investigations using Banverket´s Rolling Stiffness Measurement Vehicle (RSMV) equipped withGPR, and a methodology of comprehensive evaluation of all relevant available information have beentested on a few railway lines in Sweden since 2002. Results from these investigations are used forassessment of the root cause of existing or possible future problems with repeated track maintenance,settlement and stability when upgrading a track for higher axle load and/or speed.

The paper presents practical results of investigations and a new methodology to evaluate several types ofmeasurements in comparison with real track – substructure conditions. Suggestions on upgradingactivities are given for a case study of 25 km of track with a planned increase of axle load from 22.5 to 25metric tons. The goal is to minimize the upgrading and maintenance cost in a Life Cycle Cost (LCC)perspective.

National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10351 (URN)
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-20Bibliographically approved
5. Measurements of track stiffness and track irregularities todetect short waved support conditions
Open this publication in new window or tab >>Measurements of track stiffness and track irregularities todetect short waved support conditions
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.

National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10352 (URN)
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-20Bibliographically approved
6. A new approach to the analysis and presentation of vertical track geometry quality and rail roughness
Open this publication in new window or tab >>A new approach to the analysis and presentation of vertical track geometry quality and rail roughness
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.

Keyword
Dynamic train–track interaction; Rail roughness; Track geometry quality
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10353 (URN)10.1016/j.wear.2008.01.029 (DOI)000258891700044 ()
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2017-12-13Bibliographically approved
7. Efficient Track Maintenance -Methodology for Combined Analysis of Condition Data
Open this publication in new window or tab >>Efficient Track Maintenance -Methodology for Combined Analysis of Condition Data
2009 (English)In: International Heavy Houl Conference: Shanghai 2009, 2009Conference paper, Published paper (Refereed)
Abstract [en]

Measured condition data may contain lots of information which is not efficiently used. By usingtechniques from the field of pattern recognition, this paper outlines a methodology for eliciting newinformation. The methodology is demonstrated on a large set of condition data originating from trackgeometry quality, dynamic stiffness and ground penetrating radar. The case study gives evidence for theimportance of dynamic stiffness measurements as to determine soil and embankment related track problems,while problems originating from the upper part or the track structure do not benefit significantly.

Keyword
Condition data, Pattern recognition, Dynamic stiffness
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10354 (URN)
Note
Submitted QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-20Bibliographically approved
8. A Study of the Effect of Global Track Stiffness and its Variations on Track Performance: Simulation and Measurement
Open this publication in new window or tab >>A Study of the Effect of Global Track Stiffness and its Variations on Track Performance: Simulation and Measurement
2009 (English)In: International Heavy Haul Conference: Shanghai 2009, 2009Conference paper, Published paper (Refereed)
Abstract [en]

This paper investigates the effect of vertical track stiffness, and its variations along the track, on track performance with focus on dynamic responses of track due to parametric excitations. Two approachesfor calculating global track stiffness, a static one based on Zimmermann’s theory, and a dynamic one basedon the track model used in the dynamic vehicle-track interaction program DIFF, are discussed. A RollingStiffness Measurement Vehicle (RSMV) has been developed at Banverket and measurements have been carried out over hundreds kilometre long tracks. This paper presents a statistical analysis of the collected results and provides information of track stiffness and its variation on typical Swedish tracks.

Keyword
Track stiffness, vehicle-track interaction, rolling stiffness measurement vehicle (RSMV)
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10355 (URN)
Note
Submitted QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-20Bibliographically approved

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