Large track deflection indicates reduced track structural integrity. ⢠Track ... Deterioration of Track. Superstructure. Mode 1. Inadequate. Ballast. Strength. Mode 2.
Measurement of Track Support and Associated Track Performance Effects Ted Sussmann | U.S. DOT/Volpe Center and University of Hartford
Gary Carr, Yu-Jiang Zhang, and Hugh Thompson | U.S. DOT/Federal Railroad Administration
Motivation
Problem / Question
Track Support Indicators
Link Talbot Reports era knowledge of track deflection influence on track structure performance to track failure modes.
Measurement Method
Large or Method 1: Variable On-Board Deflection Deflection Large or Method 2: Variable Stationary Load-Deflection Deflection Abnormal Method 3: Deflection Falling Weight Basin
Hypothesis • Large track deflection indicates reduced track structural integrity • Track Deflection can be used to diagnose track conditions associated with hypothesized failure modes
Project Overview The goal of this research is to increase safety by reducing track support caused derailments. The industry trend toward higher loads has stressed
“The higher variation of seating deflections is consistent with the highly fouled condition of the ballast, whereas the high variation of contact deflection is indicative of the variability of subgrade support.”
existing infrastructure. Innovative technologies have been applied to
Method 4: Seismic Wave
N/A
Large Deflection Variable Void Deflection Large Deflection
Large Deflection
Large Void
N/A
Low Ballast Resilient N/A Modulus
Large Deflection Large Contact Deflection Large Deflection Low Subgrade Resilient Modulus
Summary and Conclusions • Large track deflection indicates track structure weakness • Track support influences the performance, structural integrity, and safety of the superstructure • Roadbed Settled/Soft is a persistent derailment cause code
quantify the condition of the track support structure. These measurements
Hypothesized Failure Modes
can provide a unique quantification of the track structural integrity that can be used to assess track substructure safety and the influence of the
Mode 2: Failure Mode 3: Mode 4: Mode 1: Mode Superstructure Inadequate Unrestrained Foundation Ballast Track Failure Degradation Strength
Mode 1
Mode 2
Mode 3
Mode 4
substructure on superstructure component performance and safety.
• No structural measurement or inspection targets support failure • Structural support inspection like deflection is the only way to diagnose support failure • Structural assessment required to drive estimates of future settlement/stability • On-board deflection testing provides indication of various failures • No diagnosis of distinctions between potential failure modes
Terminology
• In-place testing techniques supports diagnosis of various failures
Failure or Deterioration of Track Superstructure
Inadequate Ballast Strength
Unrestrained Track or Rail due to Settlement
Foundation Failure
• Provides data more directly applicable to structural performance models
Works Cited Hay, W. W. Railroad Engineering. Second Edition, John Wiley and Sons, New York, 1982. Zhang, Y. J., Murray M., and Ferreira L. (1998). Effects of substructure on track performance. Proceedings of Conference on Traffic and Transport Studies, ICTTS,1998, pp. 850-859.
Track Structural Support Inspection Method 1
Method 2
Method 3
Method 4
Lane, J., Taylor, G., Evans, E., O’Brien, A., and Ringo, T. The Contribution of Earthworks to Track Damage, World Congress on Railway Research, Milan, Italy, 2016. Li, D., Hyslip J.P., Sussmann T.R., Chrismer, S.M. Railway Geotechnics. CRC Press/Taylor & Francis Group, Boca Raton, FL, USA. 2015. Selig E.T. and Waters J.M. Track Geotechnology and Substructure Management. Thomas Telford; 1994. Sussmann, T. R., Ebersöhn, W., and E. T. Selig. Fundamental Nonlinear Track LoadDeflection Behavior for Condition Evaluation. Transportation Research Record, 1742, 2001.
On-Board Deflection Measurement
Stationary Quasi-Static LoadDeflection Test
Falling Weight Deflectometer or Lightweight Deflectometer
Seismic Wave Analysis for Track Substructure Stiffness
Berggren, E., Kaynia, A., and B. Delbom. Identification of Substructure Properties of Railway Tracks by Dynamic Stiffness Measurements and Simulations. Journal of Sound and Vibration, Vol. 329, No. 19, 2010. Farritor, S. and M. Fateh. Measurement of Vertical Track Deflection from a Moving Rail Car. Report Number DOT/FRA/ORD-13/08, U.S. DOT/FRA, 2013. Azari, H., Yuan, D., Nazarian, S., Stark, T.D., Ho, C.L., and Dehlin, T.J. Surface wave testing for characterization of ballast and foundation layers. Proceedings of 2014 JRC.
