Technical Reports

Measurement of Vertical Track Deflection from a Moving Rail Car

  • 22
  • Feb
  • 2013
AUTHOR: Shane Farritor and Mahmood Fateh
SUBJECT: Track, Tracks & Structures, Track/Train Interactions
KEYWORDS: Vertical track deflection, track deflection, rail deflection, track measurement system, vertical track modulus, track modulus, track stiffness, track geometry measurement
ABSTRACT: The University of Nebraska has been conducting research sponsored by the Federal Railroad Administration’s Office of Research and Development to develop a system that measures vertical track deflection/modulus from a moving rail car. Previous work has suggested the system can find critical maintenance problems not found by other inspection methods including standard track geometry. The University of Nebraska system uses cameras and lasers to measure a portion of the track deflection basin, and this measurement is used to estimate vertical rail deflection and/or track modulus. This report presents the measurement system along with development of the theory behind the measurement to support diagnosis of track conditions. The results of significant field testing are presented, including the results of a test designed to verify the accuracy of the measurement. A Finite Element Analysis of the measurement is presented along with several variations on closed form solution analysis, based on beam on elastic foundation as well as a discrete support model for rail. The University of Nebraska system has identified several critical maintenance problems not found by other inspection methods, and all previous studies indicate that measuring track deflection provides unique and valuable insight to track conditions that can improve inspection, maintenance, and safety. Finally, some guidelines are suggested for development of thresholds to guide data interpretation and track condition assessment, but more study and tests are needed to better define threshold criteria.