Investigation on Influences of Rail Support System on Railway Track Structural Behavior

Although the current analysis and design of railway track systems are based on theassumption of continuous and linear behavior of the rail support system, repair andmaintenance plans have considerable influences on the structural behavior of thetrack support system, particularly after accumulative loading or track tamping.Recent experimental investigation indicated the behavior of the track support systemis time and stress dependent. The amount of traffic passed and the quality andquantity of maintenance activities can considerably influence the track responsefunctions. Although some experimental investigations have been carried out to studythe time and stress dependent characteristics of the ballast and subgrade materials,the effects of the consideration of these characteristics on the track analysis anddesign, need further evaluations. Furthermore, the recent extensive increases in axleloads, speed and traffic volumes in rail transport systems, require more preciseanalytical and mechanistic approaches for railway track system. This research is aresponse to this need. In this paper, the current practices in the analysis and design ofrailway track system are discussed. A mode of track support system withconsideration of discrete supports is developed. By comparison of the analysesresults obtained from track models with continuous and discrete support systems, theaccuracy of the assumption made in the Winkler model, used in the current designapproach, are evaluated. The nonlinear behaviors of the track support system werestudied and the influences made by the consideration of the non-linearity of the tracksupport system on the rail design criteria were investigated. Rail bending momentsand rail deflections as the main rail design criteria are obtained form track with alinear support and nonlinear behaviors. Obtaining large discrepancies between theresults obtained from linear and non-linear analyses, the importance of the trackregular and systematic repairs, in particular tamping and stabilizing the ballast, areproved. It is shown that the consideration of regular repairs of the track supportsystem improves the long term reliability and accuracy of the current track designapproach. Recommendations are made on the track maintenance and repairs in orderto keep the track support system in the linear conditions.