W1 tracks kirse jb

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W1 tracks kirse jb

  1. 2. By: Ken Kirse Civil Engineer, TriMet
  2. 3. Light Rail Track Design <ul><li>Wheel-Rail Interface </li></ul><ul><li>Track Design </li></ul><ul><li>Light Rail Track Materials </li></ul><ul><li>Track Road Crossings </li></ul><ul><li>Drainage </li></ul><ul><li>Special Trackwork </li></ul><ul><li>Noise and Vibration </li></ul><ul><li>Electrical Isolation </li></ul>
  3. 4. Wheel – Rail Interface <ul><li>Wheels </li></ul><ul><li>Where does flange go </li></ul>
  4. 9. Why are flanges on the inside of wheels?
  5. 10. Rail Sections <ul><li>“ Tee” Rails </li></ul><ul><li>Girder Rails </li></ul>
  6. 16. Curving Characteristics <ul><li>With solid axles </li></ul><ul><li>With stub axles </li></ul>
  7. 19. Track Design <ul><li>Gage </li></ul><ul><li>Tie and ballast open track </li></ul><ul><li>Basis of design of tie and ballast track </li></ul><ul><li>Embedded on paved track </li></ul>
  8. 25. Modulus of Track Elasticity (  ) <ul><li>Defined as the load per unit length of rail required to depress that rail by one unit. </li></ul><ul><li>p = -  y </li></ul><ul><li>p = upward pressure per unit length </li></ul><ul><li> = track modulus of elasticity (track stiffness) </li></ul><ul><li>y = vertical deflection of rail </li></ul><ul><li>  with wood ties  = 2000 Avg., 1000 poor, 5000 stiff </li></ul>
  9. 26. Maximum Deflection Y 0 of Rail <ul><li>Y 0 = maximum deflection (x=0, under wheel) </li></ul><ul><li>p = Dynamic wheel load (static load + 1% per MPH over 5 MPH) </li></ul><ul><li> = Modulus of elasticity of rail steel (30 x 10 6 psi) </li></ul><ul><li> = Moment of Inertia of rail (65.6 in 4 for 115RE) </li></ul><ul><li>= Track modulus of elasticity </li></ul><ul><li>  AREMA recommended limit of deflection is 0.25” </li></ul>Y 0 = p (64  3 ) ¼
  10. 27. Maximum Rail Bending Moment (M 0 ) M 0 = p  64  ¼
  11. 28. Maximum Rail Bending Stress C = distance in inches from the base of rail to its neutral axis AREMA recommended maximum = 25,000 psi Rail steel yield point = 70,000 psi M 0 C  S =
  12. 29. Ballast Pressure Under Centerline of Tie (P C ) P a = uniformly distributed pressure over the tie face h = depth below bottom of tie in inches P c of 20 psi is AREMA suggested value for firm subgrade soil. P C = 16.8 P a h 1.25
  13. 30. Unit Pressure (P a ) Transmitted from Bottom of Tie to Ballast (psi) P = wheel load (lbs) 2P = Total tie load L = Tie length in inches b = Tie width in inches 2/3 = factor for 2 load bearing thirds of tie P a should not exceed 65 psi for wood ties 85 psi for concrete ties P a = 2P 2/3 bL 3P bL =
  14. 31. Rail Stress from Temperature Change 115RE rail Area = 11.2465 sq.in. Moment of Inertia about neutral axis  = 65.9 Yield Strength 70,000 psi min. Modulus of elasticity “E” 30x10 6 psi To determine tensile force for temperature change. Rail changes 0.0000065 of its length per degree. F S = unit stress . 0000065  t = S 30,000,000
  15. 32. Rail Stress from Temperature Change For 70  F change Total Restraining Force F = 70x195 x 11.2465 F = 153,515 lbs Yield Point of 115 # Rail 70,000 x 1102465 = 787,255 lbs Insulated Joints tested to 600,000 lbs For 1  F change S = 30,000,000 x 0.0000065x1 = 195 psi
  16. 35. Embedded Track <ul><li>Aesthetics </li></ul><ul><li>Maintenance considerations </li></ul><ul><li>Concrete track slabs </li></ul><ul><li>Covered tie and ballast track </li></ul>
  17. 45. <ul><li>Common on bridges </li></ul><ul><li>DF fasteners </li></ul><ul><li>Methods of construction </li></ul>Direct Fixation Track
  18. 49. Material for Light Rail Track <ul><li>Ties </li></ul><ul><li>Bumping posts </li></ul><ul><li>Switch heater </li></ul><ul><li>Switch stands </li></ul><ul><li>Insulated joints </li></ul><ul><li>Automatic train stop </li></ul>
  19. 60. Light Rail Track Road Crossings <ul><li>Design considerations </li></ul><ul><li>Crossing materials </li></ul><ul><li>Drainage </li></ul>
  20. 63. Light Rail Track Drainage <ul><li>Open track under drains </li></ul><ul><li>Paved track drainage </li></ul><ul><li>Special Trackwork Drainage </li></ul>
  21. 66. Special Trackwork <ul><li>Definition of turnout components </li></ul><ul><li>Turnout size, frog number </li></ul><ul><li>Frog types </li></ul><ul><li>Girder rail turnouts </li></ul><ul><li>Rail crossings, restraining rail </li></ul>
  22. 77. Noise and Vibration <ul><li>Problem Areas </li></ul><ul><li>Tri-Met history with Westside Project </li></ul><ul><li>Noise and vibration mitigation </li></ul>
  23. 78. P49
  24. 80. P51
  25. 81. P52
  26. 89. Electrical Isolation <ul><li>Causes of stray current </li></ul><ul><li>Why is stray current a problem? </li></ul><ul><li>Methods of controlling stray current </li></ul><ul><li>Monitoring stray current </li></ul>

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