Dynamic vehicle-track interaction with multiple short rail defects over long wavelength track settlement

Daily, hundreds of millions of train journeys are operated around the world. Trains are running on tracks at a wide range of speeds, causing dynamic effects onto track systems. The dynamic interactions between vehicle and track impose vibrations and acoustic radiations and become moving vibro-acoustic sources along the railway corridor. Especially when there is imperfection of either wheel or rail, the dynamic amplification of loading conditions and reflected vibration effects on infrastructure and rolling stocks is significantly higher. Therefore, dynamic resistance of every component (derived from dynamic testing of materials and structure) is vital in improving dynamic performance of track system. In real life, imperfection of rail tracks is inevitable and can be classified into short wave length and long wave length defects. The short wavelength defects include high-frequency related rail surface defects such as dipped joint rails, rail squats, rolling contact fatigues (RCFs), rail gabs and crossing nose. The long wavelength defects are those associated with low frequency vibrations such as differential track settlement, mud pumping, bridge ends, stiffness transition zone, etc. Most previous studies into vehicle-track interactions are concerned only to a single discreet defect individually. This study is the world first to evaluate the coupling dynamic vehicle-track interactions over coupled multiple short and long wavelength rail defects. The vehicle model has adopted multi degrees of freedom coupling with a discrete supported track model using Herzian contact theory. The validated multi-body simulations have been used to investigate the effects of the multiple short defects (e.g. multiple squats or continuous RCFs). This paper highlights the dynamic impact load factors experienced by railway track components due to wheel/rail contacts. The insight into the dynamic amplification will enable predictive track maintenance and risk-based track inspection planning to enhance public safety and reduce unplanned maintenance costs.