Transcription of Introduction to Railroad Track Structural Design
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BCR2A 09 Railroad Track Design Including Asphalt Trackbeds Pre-Conference WorkshopIntroduction to Railroad Track Structural DesignDon Uzarski, , Vertical Load Distribution, and DeflectionsComponents do not function independently!Each component layer must protect the one Distribution3 Deflection ProfileSource: Selig and Waters, Track Geotechnology and Substructure management , 19944 Static vs. Dynamic Loads Dynamic loads higher Acceleration from speed Downward rotation of wheel Smaller wheels, faster rotation, more acceleration Speed/wheel influence Pv= P + P (AREMA)wherePv= Vertical Dynamic Load (lbs) = D33x VDwx 100D = Wheel diameter (in)V = Speed (MPH)P = Static Load (lbs) Larger wheels impose less influence Additional dynamic loads from impacts such as caused by wheel flat spots, rail discontinuities ( frog flangeways), Track transitions ( bridge approaches), Track condition, Wheel Diameters38 inches28 inches36 inches33 inches36 inches6 Track Stiffness Rail is assumed to be a beam on an elastic foundation Modulus of Track Elasticity, u (or k) ( Track Modulus)u = P/ whereu = Modulus of Track Elasticity (lbs/in/in)P = Wheel load per unit length of rail (lbs/in) = Unit of Track Deflection (in)
Always consider economics! 18 Track Deflection vs. Track Performance Source: Hay, W.W., Railroad Engineering, 1982 ... – S varies by wood specie (e.g., 1000 psi for shortleaf yellow pine, 1200 psi for longleaf yellow pine, 900 psi for douglas fir, and ... Source: Selig and Waters, Track Geotechnology and Substructure Management, 1994. 36 ...
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