Technical Reports

Organization of a Simple Dynamic Model of a Railroad

  • 26
  • Nov
  • 1969
AUTHOR: John S. Mixson, Roy Steiner
OFFICE: RPD
REPORT NUMBER: FRA-RT-72-04
SUBJECT: Track
KEYWORDS: Dynamic Model, Simulation, Vibration Response, Track Roughness, Ride Quality, High-Speed Railroads
ABSTRACT: This investigation was concerned with techniques for determining values of damping and spring constants that would minimize the vibrations transmitted from irregular railroad track to passenger positions. Results developed for a three degree- of-freedom model using a simplified representation of measured track roughness illustrate the influence on the minimizing values of the type of input used, the minimization criteria adopted, and the position at which vibrations were minimized. The results were sensitive to variations of the spectrum of the input, suggesting the importance of measuring actual track irregularities and of using the measured data in optimization studies. Different results were obtained when the rms acceleration was minimized than when peak value of spectral density was minimized, suggesting that the effects on passenger comfort of overall acceleration level be compared with the effect of vibrations that are concentrated near a single frequency. Results obtained by varying the suspension stiffness of a heavy electrical transformer suspended beneath the center of the particular type of railroad car suggest that such heavy components can be tuned to improve the vibration transmission characteristics of the system.

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