A/Prof Alex Remennikov

1. Research on Railway Sleepers Down Under International Concrete Crosstie & Fastening System Symposium RailTEC, University of Illinois at Urbana-Champaign A/Prof Alex Remennikov University of Wollongong, NSW Australia

2. Introduction Country Rail Network – ARTC / JHR

3. Cooperative Research Centre CRC for Rail Innovation Core Industry Partners: Ralcorp, QR, ARA, ARTC, and Rio Tinto Iron Ore. Phase II: 2007-2013 Universities: UoW, Monash, CQU, UQ, QUT, and UniSA >$100M Funding & 5 R&D Themes

4. Cooperative Research Centre Economics, social, & environment Commercialisation & utilisation Operations & safety Engineering & safety Education & Training 4

5. Ballast - Fouling Effect of Ballast Fouling  subgrade pumping  coal  high ballast abrasion field investigation at Bellambi 5

6. Ballast – Impact load Effect of Impact loads on ballast degradation  ballast breakage impact load   track stability ballast breakage 6

7. Ballast – Impact load Effect of Impact loads on ballast degradation  ballast breakage impact load   track stability ballast breakage 7

8. Ballast - NDT NDT for Ballast Quality  ballast breakage  track resilience  fine particle contamination rail sleeper ballast layer subballast formation

9. Ballast - NDT

10. Rail Squats Rail Squat Strategies  field investigation UQ/Monash/CQU  finite element analysis  metallurgical studies damage of components

11. Short Pitch Irregularities Detection of Short Pitch Irregularities CQU  vibration based detection using AK Car axle box data   integration algorithm dipped welds

12. Turnouts & Crossing Reduction of Impact due to crossing and turnouts Field Trials Sleeper/bearer pads Composite bearers

13. Concrete Sleepers Projects Innovative/Automated Track Maintenance and Upgrading Technologies Dynamic analysis of track and the assessment of its capacity with particular reference to concrete sleepers Key Industry Partners 13 I ntroduction RAIL CRC

14. IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG? • Concrete sleepers are designed according to a 19th century deterministic method called ‘permissible stress design’ (e.g. AS1085.14-2009, AREMA Manual for RailwayEngineering (2010). 14 I ntroduction RAIL CRC

15. IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG? • Today almost all structural codes around the world use limit states design (aka Load and Resistance Factor Design LRFD), except for codes used in the design of concrete railway sleepers. 15 I ntroduction RAIL CRC

16. IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG? • There is a widespread perception in the railway industry that concrete sleepers have unused reserves of strength. • E.g., sleepers are generally replaced only because of non-design factors such as serious damage due to train derailment or inappropriate materials in the concrete mix or manufacturing faults. 16 I ntroduction RAIL CRC

17. IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG? • If concrete sleepers have unused reserve strength, increases in axle loads & train speeds may not, for example, need sleepers to be replaced with heavier ones. • The saving in expenditure around AU$100,000 per km of track could be achieved if the 22t sleepers in that section of track are found to not need replacing with higher rated sleepers. 17 I ntroduction RAIL CRC

18. IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG? • The current design approach is not wrong, but there is clearly a need for a method of designing and rating of concrete sleepers that is more rational than permissible stress design and which allows for the inherent variability of strength and of applied loads. • Development of the framework for designing concrete sleepers using limit states approach is discussed in this presentation. 18 I ntroduction RAIL CRC

19. Limit States Design Framework for Prestressed Concrete Sleepers 19

20. LIMIT STATES CONCEPT Limit state deems that the strength of a structure is satisfactory if its calculated nominal capacity, reduced by a capacity factor , exceeds the sum of the nominal load effects multiplied by load factors . ×Nominal load effects ≤ ×Nominal capacity where the nominal load effects (e.g. bending moments) are determined from the nominal applied loads by an appropriate method of structural analysis (static or dynamic). 20 L imit states design RAIL CRC

21. PROPOSEDLIMIT STATES OF PC SLEEPERS A single once-off event such a severe wheel flat that generates an impulsive load capable of failing a single concrete sleeper. Failure under such a severe event would fit within failure definitions causing severe cracking at the rail seat or at the midspan. ULTIMATE A time-dependent limit state where a single concrete sleeper accumulates damage progressively over a period of years to a point where it is considered to have reached failure. Such failure could come about from excessive accumulated abrasion or from cracking having grown progressively more severe under repeated loading impact forces over its lifetime. FATIGUE This limit state defines a condition where sleeper failure is beginning to impose some restrictions on the operational capacity of the track. The failure of a single sleeper is rarely a cause of a speed restriction or a line closure. However, when there is a failure of a cluster of sleepers, an operational restriction is usually applied until the problem is rectified. SERVICE-ABILITY 21 L imit states design RAIL CRC

22. DEFINITION OF A “FAILED” SLEEPER Australian railway organisations would condemn a sleeper when its ability to hold top of line or gauge is lost. abrasion at the bottom of the sleeper causing a loss of top; abrasion at the rail seat causing a loss of top; severe cracks at the rail seat causing the ‘anchor’ of the fastening system to move and spread the gauge; severe cracks at the midspan of the sleeper causing the sleeper to ‘flex’ and spread the gauge; Only severe cracking leading to sleeper’s inability to hold top of line and gauge are considered as the failure conditions defining a limit state. 22 L imit states design RAIL CRC

23. Limit States Design and In-track Loads 23

24. Data Collection • In limit states design the actual spectrum of forces is needed and in-field measurements are required. • 12 months of WILD wheel impact data has been gathered from QR sites at Braeside & Raglan in Central Queensland. • Approximately 5 million measurements of impacts means data is statistically robust. 24 RAIL CRC

25. Data Analysis Variability of wagon weight for the nominal 28t (2 x 137 kN) axle loads. Mean force is 128 kN, standard deviation 13 kN. 25

26. Data Analysis Straight line means forecast of impacts is reliable beyond the 12 months of data 26

27. Other Factors Affecting In-Track Loads 27

28. Experimental Investigation of Dynamic Ultimate Capacities of Prestressed Concrete Sleepers for Limit States Design 28

29. DYNAMIC TESTING PROCEDURE Drop hammer impact testing machine Frame height = 6m Falling mass = 600 kg Impact load up to 2000 kN Impact velocity up to 10 m/s Operation efficiency 98% Working area = 5x2.5m 29 T esting RAIL CRC

30. DYNAMIC TEST SETUP Overall view Railseat section 30 T esting RAIL CRC

31. DYNAMIC TEST SETUP (VIDEO) 31 T esting RAIL CRC

32. DYNAMIC TEST SETUP (VIDEO) 32 T esting RAIL CRC

33. IMPACT RESISTANCE OF SLEEPERS Impact forces between 500kN and 1600kN 33 T esting RAIL CRC

34. IMPACT RESISTANCE OF SLEEPERS Impact failure of low profile sleeper at 1400kN 34 T esting RAIL CRC

35. IMPACT RESISTANCE OF SLEEPERS Crack development under repeated loads 35 T esting RAIL CRC

36. Proposed Ultimate Limit State Design Equations: (based on Murray and Bian (2011)) where MQ is the moment induced in the sleeper by the design value of the wagon weight force; MI is the moment induced in the sleeper by the ultimate impact force I for the specified return period; 36

37. Experimental Determination of Impact Load – Railseat Moment Relationship 37

38. Numerical Determination of Impact Load – Railseat Moment Relationship 38

39. Case Study: Evaluate the Capacity of the Existing Concrete Sleepers to Carry Double Traffic Volume over next 10 years Analysis based on working stress method Analysis based on ultimate limit state method 39

40. CONCLUSIONS Extensive investigations at UoW within the framework of the Rail-CRC have addressed the spectrum and magnitudes of dynamic forces, the reserve capacity of typical PC sleepers, and the development of a new limit states design concept. The proposed methodology has been successfully applied to the problems involving increased traffic volume and increased axle loads where the untapped reserve capacity allowed to not replacing the existing concrete sleepers with higher rated sleepers. 40 C onclusions RAIL CRC

41. Thank you for your attention Questions & Answers Q&A