DETERMINATION OF LONGITUDINAL AND TRANSVERSE RAILWAY TRACK RESISTANCE

Several national guidelines set the non-linear horizontal spring values between the railway track and a railway bridge. In Finland that is not the case. Consequently, one of the objectives of the research funded by the Finnish Rail Administration was to determine the spring values both during the elastic phase in the beginning of displacement and during the plastic phase. These values are needed, for example, to calculate the behaviour of an integral bridge-track structure. In autumn 2007 researchers from the Department of Civil Engineering at Tampere University of Technology performed field tests to measure the track resistance at a railway yard in Mellila, Finland. The main objectives of the experimental study were 1) to determine the longitudinal track resistance and the load-displacement relation, 2) to compare the measured values to those reported by the International Union of Railways (UIC), and 3) to determine the transverse track resistance and the load-displacement relation. The railway yard had three track test locations, two for longitudinal loading and one for transverse loading. At each location the rails were cut to a length of six to seven metres. During the longitudinal loading the track was loaded with two adjacent hydraulic jacks. Altogether eight longitudinal tests were conducted, three without a vertical load and five with a vertical load. The vertically unloaded track reached the plastic phase due to the axial load. The vertically loaded rails moved axially in their fasteners while the sleepers moved only a little in relation to them. Consequently, the track did not reach the plastic phase. The results of the longitudinal tests were reported as horizontal and vertical displacements and axial rail stresses along the rail at different phases of the axial loading. The results were presented also in tables where initial stage stiffness was presented as an elastic value [kN/m/m] and plastic track resistance in kN/m. The maximum forces per metre affecting the track without a vertical load were 13 to 15 kN/m. The maximum forces per metre affecting the track with a vertical load were 26, 15 and 31 kN/m. During transverse loading the track was loaded horizontally with an excavator bucket. Altogether five loadings with three different arrangements were performed. The loadings clearly caused curvature of the track. The results of the transverse tests were reported as displacements at different locations during different phases of loading.