ON THE MEASUREMENT AND CALCULATION OF VERTICAL TRACK MODULUS

This paper presents the results of a series of tests and analyses directed towards the characterization of the track structure under vertical loads. It also presents and evaluates different analytical techniques for the calculation of the vertical track modulus. In a series of tests at the Association of American Railroads's Track Structures Dynamic Test Facility, the response of the track was obtained by monitoring track deflection under increasing vertical loads. This load and deflection data was then used to calculate vertical track modulus, track stiffness and track compliance. Three widely used techniques were utilized to calculate the vertical modulus. The results of the tests indicate that the modulus of the track is related to the level of loading; thus identical track can give different modulus values for different load levels. Of the three different techniques used to calculate track modulus, the beam-on-elastic-foundation technique was found to be the most applicable to field measurements since it requires a minimum number of track deflection values.