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1Remaining Life of Concrete Sleepers: A Multifaceted ApproachA/Prof Alex RemennikovSchool of Civil, Mining and Environmental EngineeringUniversity of Wollongong, NSW, Australia

University of WollongongIntroduction2This 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.2Three-Pronged Characterisation Approach3Loading Characterisation for Railway TrackTypical wheel impact detector (WID) data as-received5

Static loads (extracted from WID data)6

Impact loads (extracted from WID data)7

Impact load curve fitting8

1:101:1001:1000Impact load, forecasting9

Strength Characterisation for Concrete SleepersSTATIC TESTS11Rail seat vertical load tests Negative and Positive Bending Moments

Centre Negative and Positive Bending Moment Tests11DYNAMIC TESTING12Concrete 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 kNMonitoring equipment: Dynamic load cell Laser displacement sensors Accelerometers Strain gauges High-speed camera12DYNAMIC TESTING13Impact tests setup

Falling anvil 600 kgShock absorbersStrong floorTested concrete sleepersSleeper support systemOptical trigger13DYNAMIC TESTING14Impact 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)Strong Concrete Floor (1.5 m deep)Ballast (150 mm)Shock mat (10mm)Shock mat (10mm)

14VERIFICATION OF PRESTRESSING15Test arrangement and instrumentation

Specimens prepared for dynamic relaxation tests at sleeper centre

Strain gauges attached to steel wires

Wire cutting and data recording procedure15TYPICAL RESULTS STATIC TESTING16Rail Seat Bending Strength

16TYPICAL RESULTS STATIC TESTING17Centre Bending Strength

17TYPICAL SUMMARY OF STATIC TEST RESULTS18Type of testSleeper marksCracking load (kN)Cracking moment (kN.m)Ultimate load capacity (kN)Ultimate moment capacity(kN.m)Design moment capacity (kN.m)1Centre positive moment (MC+)UOW17830.0993838UOW28532.699382Centre negative moment (MC-)UOW38532.61044040UOW411042.2138523Rail seat positive moment (MR+)UOW535057.85759595UOW635057.8580964Rail seat negative moment (MR-)UOW715024.84206958UOW815024.83505818RESULTS IMPACT TESTING19Hard Track Support ConditionExperimental setup

High-speed camera for recording short duration impact event19RESULTS IMPACT TESTING20Hard Track Support ConditionHigh-speed camera recording

20RESULTS IMPACT TESTING21Hard Track Support ConditionImpact testing program (based on predicted impact load from spectral analysis of WILD data)Test NoDrop height (mm)Maximum load (kN)Loading duration (msec)Observed damage191060614no damage291057015no damage391561513no damage491562514first minor crack 591558014crack propagation691559014no additional damage791563713no additional damage891561313no additional damage991563013no additional damage1091563014no additional damage11102570013no additional damage

Sleeper deformation from image processing21RESULTS IMPACT TESTING22Hard Track Support ConditionCracking at rail seat

Ballast crushing due to high impact loads22RESULTS LEVEL OF PRESTRESS23Dynamic relaxation testsLevel of prestress for undamaged sleeper is

Sleepers with damaged end and exposed steel wires

Level of prestress for damaged sleeper is23Material Characterisation for Concrete SleepersMaterial Characterisation for Concrete Sleepers

Concrete Strength

Ultrasonic Pulse Velocity

Carbonation testingMaterial Characterisation for Concrete SleepersLevel of Chloride at strand depthAlkali Silica Reaction Delayed Ettringite Formation/Sulphate Attack

Future Research Objectives:27To 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