Railway track inspection and maintenance priorities due to dynamic coupling effects of dipped rails and differential track settlements

Each year, there can be three to six millions of service train axles running over an open plain track. In fact, these trains could impose a variety of dynamic loading conditions depending on the wheel and rail maintenance levels. Inevitably, the risk of high-intensity dynamic loading conditions by wheel-rail interactions due to wheel or rail irregularity cannot be disregarded. Imperfection of rail tracks could lead directly to the exceedance of permissible stress of a track component and later amplify rapid track deterioration rates causing cracking in sleepers and failure of track substructure. Practical railway track irregularities can be typically classified into short wave length (high frequency) and long wave length (low frequency) defects, of which previous researchers had studied each in isolation. This paper is the first to study the influence on railway track inspection and maintenance priorities caused by the coupling of wave lengths between dipped rail joint and differential track settlements. To study the dynamic coupling effects, P1 and P2 forces are evaluated at the track irregularity together with rail/sleeper contact force, ballast pressure and bending moments of sleepers using dynamic multi-body simulation approach. It is found that some patterns of coupling irregularity could cause a significant reduction in dynamic impact factors whilst some are associated with an increase in the wheel/rail impact force. The insight has then been integrated to establish track performance indicators that are paramount for prioritising track inspection and maintenance.