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Agenda

Agenda. Study of elastic under tie pads Measuring of lateral resistance of conventional ties and with under tie pads in both laboratory as well as in real operational tracks Application of the recorded parameters to F EM. Determination of bedding modulus of elastic tie pads.

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Agenda

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  1. Agenda • Study of elastic under tie pads • Measuring of lateral resistance of conventional ties • and with under tie pads in both laboratory as well as in • real operational tracks • Application of the recorded parameters to FEM

  2. Determination of bedding modulus of elastic tie pads Standard Ballast Plate (SBP) Even Plate TUM-Plate with glued real ballast stones Geometric Ballast Plate (GBP)

  3. Determination of bedding modulus of elastic tie pads 20 cm Concrete SBP on smaller specimen (300x300 mm) SBP on bottom side of tie on ties in ballast bed

  4. Determination of bedding modulus of elastic tie pads bedding modulus decreases

  5. Minimal bedding modulus of underground and ballast 1/Ctotal = 1/Ctie pad+ 1/Cunderground+ballast +(1/Crail pad ~ 0) min Ctotal = 0.05 N/mm3 best load-distribution effect of rail 60 E2 could be activated allowable tensile stress on rail foot will not be exceeded

  6. Simulating the service loading • - Measurement of lateral resistance in consolidated condition • Contact stress between ballast and bottom side of tie

  7. Contact stress between ballast and bottom side of tie conventional B 70 B 70 with stiff tie pad (PM) B 70 with soft tie pad (G04 with fleece) conventional tie with tie under tie pad

  8. Lateral resistance of conventional ties and with under tie pads • The lateral resistance of ties with UTP depends firstly on: • Elastic material properties of UTP • Tie geometry • Properties of the ballast • Required laboratory tests: • Determination of elastic properties of the UTP • Determination of ballast properties • Determination of lateral resistance of ties with and without UTP

  9. Investigations on ballast type A (quarry A) und type B (quarry B), both class “S” Lateral resistance is positively influenced by: Lateral resistance of conventional ties and with under tie pads (EN 933-1) Far tiered grading curve High mass percentage of gravel stones > 40 mm Less fine grain < 0.5 mm Less fines < 0.063 mm (EN 933-4) Compact grain shape length : width < 3:1 (EN 1097-1) Micro-Deval-Test: high abrasion resistance (EN 1097-2) Los Angeles-Test: high impact strength - ballast type B shows better properties regarding lateral resistance as type A lateral resistance with ballast type B is about 20 % higher as with type A

  10. Lateral resistance of conventional ties and with under tie pads Determination of lateral resistance of ties B 70 in laboratory tie ballast tie pad ballast rig neutral axis Measurements in both unconsolidated and consolidated conditions Determination of static and dynamic lateral resistance Determination of lateral resistance under wet ballast conditions (rain fall) Determination of individual parts of lateral resistance

  11. Lateral resistance of conventional ties and with under tie pads Load-displacementcurve of single ties B 70 horizontal force FH (at 2 mm displacement) B 70 with G04, LVD (very soft) 8.5 kN B 70 with G04, fleece (soft) 8.1 kN B 70 with PM (stiff) 7.4 kN B 70 without tie pad 6.7 kN consolidated ballast type B horizontal force [kN] B 70 with pad G04, LVD (very soft) B70 with pad G04, fleece (soft) B 70 with pad PM (stiff) B 70 without tie pad lateral displacement of the tie [mm] • bi-linear load-displacement curve, continuouslyslope change point due to under tie pads • ties with under tie pads show a higher lateral resistance than conventional ties • - lateral resistance is increasing with decreasing of the tie pad stiffness

  12. Determination of lateral resistance in laboratory Lateral resistance of conventional ties and with under tie pads PM

  13. Determination of lateral resistance in service track Lateral resistance of conventional ties and with under tie pads • Difference of absolute values of lateral resistance due to: • Qualitative agreement of results in laboratory and service track • ballast properties and underground performance • width of front ballast • initiated tamping work

  14. Application of recorded parameters to FEM railtie structurepointsoftie structurepointsofrail

  15. Verifying FE-Model forstraighttrackfromfull-scaletestsection in Rohrbach Application of recorded parameters to method of Meier and to FEM • failureoftrackirregularity = 23 mm • lengthoftrackirregularity = 16,2 m • lateral resistance = 9,2 N/mm Verschiebeweg des Gleisrostes[mm]

  16. Verifying FE-Model forcurvedtrackwith R = 360m fromfull-scaletestsection in Daglfing Application of recorded parameters to FEM • failureoftrackirregularity = 13 mm • lengthoftrackirregularity = 16,8 m • lateral resistance = 4,4 N/mm

  17. Resultsof FEM: Influenceofserviceload on lateral trackstability Application of recorded parameters to method of Meier and to FEM TiesB 70 withtiepad G04andfleece,straighttrack • - increasingof lateral resistance • - underwheelloads • - applicationofdynamic lateral • - resistance • - consideringtheupliftwave • (reductionofbottomresistance) • - simulationoftrackconditions: • perfectconditions, rain falls, • verticaltrackirregularity, • insufficientballastingofties rail deflection [mm] lateral resis-tance

  18. Resultsof FEM regarding lateral trackstability Application of recorded parameters to FEM •  Lateral resistanceandimperfectionshavesignificantinfluence •  Lateral resistance • - ties with under tie pads are better than conventional ties • Critical imperfections • - biggertrackfailures • - lengthoftrack irregularityappr. 10 m - 12,5 m (straighttrack) • - lengthoftrack irregularityappr. 5 m (curvedtrackwith R = 360 m) • Rail profile • - smaller Cross sectionsaresaiferagainsttrackbuckling Q

  19. Conclusion • The application of elastic under tie pads has many advantages - increasingoftrackelasticityreductionofrailseatloadprotectingthe othertrackcomponents - increasingofcontactareabetweenballastandbottomsideoftie reductionofcontact stress extensionofmaintenanceinterval - allowable tensile stress on rail foot should not be exceeded - ballast deterioration on the tie sides • Elastic under tie pads should not be too soft

  20. Chair and Institute of Road, Railway and Airfield Construction Technical University Munich, Germany Univ. Prof. Dr.-Ing. Stephan Freudenstein stephan.freudenstein@vwb.bv.tum.de www.vwb.bv.tum.de

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