Technical Reports

Pilot Study for Definition of Track Component Load Environments

  • 01
  • Feb
  • 1981
AUTHOR: Thomas R. Staglianol, Lawrence J. Mentel, Edward C. Gadden Jr., Bob W. Baxter, Warren K. Hale, Russel W. Maccabe Jr.
SUBJECT: Tracks & Structures
KEYWORDS: Transit Track Design, Track Instrumentation, Transit Track Testing, Track Costs
ABSTRACT: This report describes the results of an experimental and analytical effort to define the vehicle induced load environment in an at-grade, concrete tie/ballast transit track structure. The experiment was performed on the UMTA transit track oval at TTC in Pueblo, Colorado in order to establish an initial data baseline which could be extended to include data from tests conducted on various transit track structural systems. Standard experimental techniques generally were used to measure the pressures, strains and applied wheel/rail loads in the various track structure components; however, innovations were effectively introduced for measuring pressures on the bottom of the concrete tie and in the ballast. Track design methods and analytical computer techniques for predicting the load environment in the various track components were evaluated through comparisons with the experimental data. Design conservatism in the tie/ballast transit track systems was evaluated from the aspect of stress criteria versus other design factors based on experience and initial capital costs versus maintenance costs for transit systems. It was indicated from these tests, performed on a well constructed and maintained track structure, that there exists significant conservatism based on stress criteria, but the transit industry believes that the savings on construction costs for a more optimal stress design would be overshadowed by anticipated increases in maintenance costs. It is indicated by the results of this effort that many of the design stress methods currently being used should be improved, especially in the prediction of the load environment in the ballast and subgrade. It is anticipated that the experience gained in this pilot study can be applied in defining the load environment for other transit track configurations.
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