Stochastic Response of Irregular Tracks Under Moving Vehicles

Abstract

Profile irregularity is invariably present in any railway track. Among the various causes which influence the dynamics of track-vehicle system, track irregularity is perhaps the most important, one. Profile irregularity make the moving vehicle vibrate, which in turn, induces dynamic forces on track. These forces depend also on the dynamic characteristics of moving vehicles. Under the influence of these forces, supporting subgrade yields in the regions of high stresses. This leads to further changes of the track profile. Thus dynamic forces on track and nonlinear behviour of the subgrade are the basic causes of track deterioration. Furthermore irregularities are stochastic in nature and so are the track forces. For proper understanding of track behaviour it is necessary to include vehicle characteristics and the stochastic nature of irregularities in to the analysis. In the past most of the studies have either ignored or have oversimplified track-vehicle interaction. Also there are very few studies on track deterioration. Patil (1988) and Duffy (1990) have considered the vehicle mass in the dynamic analysis of railway tracks. They studied the effect of vehicle mass on the resonant track frequency and the critical velocity. Further, it can be mentioned here that subgrade properties vary along the track and these variations are stochastic. Fryba et al. (1991) have studied the effect of these variations on the dynamic response of tracks. Most of the studies on tracks with nonlinear foundations have considered track response to a single moving force.