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Quantifying the Distribution of Rail Bending Stresses along the Track using Train-Mounted Deflection Measurements Open Access


Other title
Railway Track
Track Modulus
Rail bending stresses
Deflection measurements
Type of item
Degree grantor
University of Alberta
Author or creator
Fallah Nafari, Saeideh
Supervisor and department
Cheng, J.J. Roger (Civil and Environmental Engineering)
Gül, Mustafa (Civil and Environmental Engineering)
Examining committee member and department
Hendry, Michael (Civil and Environmental Engineering)
Walbridge, Scott (Civil and Environmental Engineering, University of Waterloo)
Li, Yong (Civil and Environmental Engineering)
Department of Civil and Environmental Engineering
Structural Engineering
Date accepted
Graduation date
2017-06:Spring 2017
Doctor of Philosophy
Degree level
Heavy and frequent train loads generate large bending stresses in rail. These stresses contribute to the propagation of transverse fatigue defects, which are among the leading causes of broken rail derailments in North America. A thorough assessment of the rail structural condition requires reliable methods for estimating rail bending stresses. This is often challenging due to the many uncontrollable environmental, operational, and structural factors that affect the magnitude of rail bending stresses along the thousands of miles of track. In this study, a new methodology was developed for estimating rail bending stresses over long distances using train-mounted vertical track deflection (VTD) measurements. Mathematical correlations between track modulus, rail deflection, rail stress, and applied load form the basis of the method. To develop the correlations, a new finite element modelling method was developed which allowed the simulation of a stochastically varying track modulus along the track. Track models with different track modulus distributions were developed and the resulting VTD and rail bending stresses under moving wheel loads were calculated. The mathematical correlations between the inputted track modulus, modelled VTD and rail bending stresses were quantified using statistical approaches. Based on the results, equations were proposed to estimate the statistical properties of track modulus and rail bending stresses over track windows using the VTD measurements. A framework was also developed to estimate the probability distributions of maximum tensile and compressive bending stresses in the rail head and base, which are necessary for calculating the rail reliability under applied loading. The accuracy of the proposed equations was first verified using a numerical case study for which a random track modulus distribution was considered and artificial noise was added to the modelled VTD. Subsequently, datasets collected from a study site were used to validate the methodology for estimating rail bending stresses. The rail-mounted strain gauges and the wheel impact load detector system at the study site provided information about the rail bending strains under known applied loads. This allowed validation of the maximum bending stresses estimated using train-mounted VTD measurements. The thesis includes recommendations for future work.
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
Citation for previous publication
Fallah Nafari S, Gül M, Roghani A, Hendry M.T, and Cheng J.J.R, Evaluating the Potential of a Rolling Deflection Measurement System to Estimate Track Modulus. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit doi: 10.1177/0954409716646404.

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