Technical Reports

Computational Methods to Predict Railcar Response to Track Cross-Level Variations

  • 01
  • Sep
  • 1976
AUTHOR: Federal Railroad Administration; B.E. Platin; J.J. Beaman; J.k. Hendrick; D.N. Wormley
OFFICE: RPD
REPORT NUMBER: FRA-ORD-76-293
SUBJECT: Track, Tracks & Structures, Track/Train Interactions
KEYWORDS: Rock and Roll
ABSTRACT: The rocking response of railroad freight cars to track cross-level variations is studied using: (1) a reduced complexity digital simulation model, and (2) a quasi-linear describing function analysis. The reduced complexity digital simulation model employs a rail truck model that neglects the high-frequency dynamics of the bolster and wheelset masses, yet includes kinematic center plate, side bearings, and wheelset nonlinear effects. This model has computation-time requirements that are less than one eighth those of more detailed computer simulation models and agrees within 15% percent for the prediction of roll angle, side bearing force, center plate force and wheel force at maximum roll angle response with the more detailed models. A study of quasi-linear describing function techniques to compute the steady-state response of freight cars to equivalent sinusoidal cross-level track variations has demonstrated the feasibility of the technique for the types of nonlinearities important in car response. This technique, which computes steady-state response from a set of nonlinear algebraic equations rather than by numerical integration, is effective for parametric studies in which a series of the responses is required as a parameter is varied incrementally since once the solution is obtained for one set of parameter values, additional responses for an incremental change in the parameter are obtained efficiently.

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