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

2. Introduction 2 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. Strength Loading Materials Static tests Impact tests Fatigue tests Prestressing tests Processing of WILD data Spectral analysis of WILD Forecasting for next 5-10 years Limit states design checks Concrete strength Cement content/w/c ratio Ultrasonic Pulse Velocity Concrete carbonation Sulphate Attack and Delayed Ettringite Formation 3

4. Collection and Processing of Wheel Impact Detectors Data Spectral Analysis of Data from WILD Extrapolation of data for next 5-10 years period Limit States Design Checks

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

6. Static loads (extracted from WID data) 6

7. Impact loads (extracted from WID data) 7

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

9. Impact load, forecasting 9

10. Static bending testingDynamic impact testingFatigue testingPrestressing tests

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

12. DYNAMIC TESTING 12 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 13 Impact tests setup Falling anvil 600 kg Shock absorbers Strong floor Tested concrete sleepers Sleeper support system Optical trigger 13

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

15. VERIFICATION OF PRESTRESSING 15 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 16 Rail Seat Bending Strength 16

17. TYPICAL RESULTS – STATIC TESTING 17 Centre Bending Strength 17

18. TYPICAL SUMMARY OF STATIC TEST RESULTS 18 Type of test Sleeper marks Cracking load (kN) Cracking moment (kN.m) Ultimate load capacity (kN) Ultimate moment capacity (kN.m) Design moment capacity (kN.m) 1 Centre positive moment (MC+) UOW17830.09938 UOW28532.69938 2 Centre negative moment (MC-) UOW38532.610440 UOW411042.213852 3 Rail seat positive moment (MR+) UOW535057.857595 UOW635057.858096 4 Rail seat negative moment (MR-) UOW715024.842069 58 UOW815024.835058 18

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

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

21. RESULTS – IMPACT TESTING 21 Hard Track Support Condition Impact testing program (based on predicted impact load from spectral analysis of WILD data) Test No Drop height (mm) Maximu m load (kN) Loading duration (msec) Observed damage 191060614no damage 291057015no damage 391561513no damage 491562514 first minor crack 591558014 crack propagation 691559014 no additional damage 791563713 no additional damage 891561313 no additional damage 991563013 no additional damage 1091563014 no additional damage 11102570013no additional damage Sleeper deformation from image processing 21

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

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

24. Concrete Strength and Modulus of Elasticity Cement Content and W/C RatioUltrasonic Pulse VelocityConcrete Carbonation Chloride Content Analysis and more

25. Concrete Strength Ultrasonic Pulse Velocity Carbonation testing

26. Level of Chloride at strand depth Alkali Silica Reaction Delayed Ettringite Formation/Sulphate Attack

27. Future Research Objectives: 27 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