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Remaining Life of Concrete Sleepers: A Multifaceted Approach

University of Wollongong. Remaining Life of Concrete Sleepers: A Multifaceted Approach. A/Prof Alex Remennikov School of Civil, Mining and Environmental Engineering University of Wollongong, NSW, Australia. Introduction.

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Remaining Life of Concrete Sleepers: A Multifaceted Approach

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  1. University of Wollongong Remaining Life of Concrete Sleepers: A Multifaceted Approach A/Prof Alex Remennikov School of Civil, Mining and Environmental Engineering University of Wollongong, NSW, Australia

  2. Introduction • This project will give track owners methods of more accurately assessing the dynamic capacity of in-track concrete sleepers. • As commercial pressures drive up axle loads and train speeds, deferring large-scale sleeper replacement through higher sleeper capacity rating has the potential for very large savings in capital expenditure for owners. • To establish better methods of sleeper rating, the method is based on in-track and laboratory-based studies of the static, dynamic and impact behaviour of sleepers, of the actual loading regimes experienced by sleepers in-track, and detailed material characterization of the concrete. 2

  3. Three-Pronged Characterisation Approach

  4. Loading Characterisation for Railway Track

  5. Typical wheel impact detector (WID) data as-received

  6. Static loads (extracted from WID data)

  7. Impact loads (extracted from WID data)

  8. Impact load curve fitting 1:10 1:100 1:1000

  9. Impact load, forecasting

  10. Strength Characterisation for Concrete Sleepers

  11. STATIC TESTS Rail seat vertical load tests – Negative and Positive Bending Moments Centre Negative and Positive Bending Moment Tests 11

  12. DYNAMIC TESTING Concrete Sleepers Impact Load Testing Facility at UoW • Characteristics: • Height of impact = 6 m • Weight of anvil = 600 kg • Max impact velocity = 10 m/s • Max impact energy = 10,000 J • Max impact load = 2000 kN • Monitoring equipment: • Dynamic load cell • Laser displacement sensors • Accelerometers • Strain gauges • High-speed camera 12

  13. DYNAMIC TESTING Impact tests setup Optical trigger Falling anvil 600 kg Shock absorbers Sleeper support system Tested concrete sleepers Strong floor 13

  14. DYNAMIC TESTING Impact tests setup – sleepers support systems for different track moduli Very soft track (8 MPa) Moderate track modulus (20-70 MPa) Very hard track (120 MPa) Ballast (200 mm) Ballast (150 mm) Sand-rubber Mix (200 mm) Strong Concrete Floor (1.5 m deep) Strong Concrete Floor (1.5 m deep) Shock mat (10mm) Shock mat (10mm) 14

  15. VERIFICATION OF PRESTRESSING Test arrangement and instrumentation Specimens prepared for dynamic relaxation tests at sleeper centre Strain gauges attached to steel wires Wire cutting and data recording procedure 15

  16. TYPICAL RESULTS – STATIC TESTING Rail Seat Bending Strength 16

  17. TYPICAL RESULTS – STATIC TESTING Centre Bending Strength 17

  18. TYPICAL SUMMARY OF STATIC TEST RESULTS 18

  19. RESULTS – IMPACT TESTING Hard Track Support Condition Experimental setup High-speed camera for recording short duration impact event 19

  20. RESULTS – IMPACT TESTING Hard Track Support Condition High-speed camera recording 20

  21. RESULTS – IMPACT TESTING Hard Track Support Condition Impact testing program (based on predicted impact load from spectral analysis of WILD data) Sleeper deformation from image processing 21

  22. RESULTS – IMPACT TESTING Hard Track Support Condition Ballast crushing due to high impact loads Cracking at rail seat 22

  23. RESULTS – LEVEL OF PRESTRESS Dynamic relaxation tests Sleepers with damaged end and exposed steel wires Level of prestress for undamaged sleeper is Level of prestress for damaged sleeper is 23

  24. Material Characterisation for Concrete Sleepers

  25. Material Characterisation for Concrete Sleepers Concrete Strength Ultrasonic Pulse Velocity Carbonation testing

  26. Material Characterisation for Concrete Sleepers Level of Chloride at strand depth Alkali Silica Reaction Delayed Ettringite Formation/Sulphate Attack

  27. Future Research Objectives: • To revise current acceptance standards for prestressed concrete sleepers based on results of impact testing for fatigue and ultimate limit state conditions. • To revise current sleeper loading prediction methodology to reflect findings from the measurement and analysis of in-track data. • To develop a sleeper acceptance framework for sleepers. • To establish a methodology for capacity rating of concrete sleepers. 27

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