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The derailment of railway vehicles in the turnout area is a worldwide concerned issue. Previous studies mainly concentrate on the derailment at the switch area, and the risk at the frog area is seldom concerned. Based on a specific derailment case of the remote locomotive in a 20,000-tonne heavy-haul train, a study on the derailment of the locomotive at the turnout frog area is presented. The conditions of the derailed locomotive and turnout track are introduced, and the potential influence factors are screened according to the field investigation results. A detailed simulation model that considers the complex wheel-frog/guard rail contact relationship and the interaction between adjacent vehicles is established. Through numerical simulation, the derailment process of the locomotive at the turnout frog area is reproduced, and the derailment mechanism is revealed, followed by the influence analysis of the potential factors. The results indicate that the combined effect of the compressive coupler force and the coupler jack-knifing promotes the derailment remarkably. Moreover, the derailment at the turnout frog area is more likely to occur under low-speed conditions, and the possibility of derailment can be reduced by decreasing the compressive coupler force and the friction coefficients between the wheel and stock/frog/guard rail. [ABSTRACT FROM AUTHOR]

Damage of rail fastening system often occurs due to severe vehicle-track dynamic interactions. To evaluate the dynamic performance of the rail fastening system subject to dynamic interactions between vehicle and track, a refined vehicle-track coupled dynamics model involving an elaborated model of rail fastening clip (RFC) is developed in this work. Firstly, the RFC model is established based on the mode superposition method by which the difficulty in deducing dynamics equation due to the complex shape of RFC can be easily resolved. Then, the mode shape vectors and natural frequencies of RFC which required by the mode superposition method are obtained through a numerical modal analysis, and verified by a modal test. Finally, through the contact relationship between RFC and rail, the RFC model is implemented into the vehicle-track coupled dynamics model. The reliability of the proposed model is supported by a field test data, and the dynamic performances of rail fastening systems along the track subject to vehicle-track dynamic interactions can be efficiently and effectively evaluated. By applying the proposed model, the influences of rail corrugations, vehicle speeds, and rail pad stiffness on dynamic performances of the rail fastening system are evaluated in detail. [ABSTRACT FROM AUTHOR]

To study the impact coefficient of track beams due to moving suspended monorail vehicles under the bridge deck, this paper presents a vehicle-bridge dynamic model based on the rigid-flexible coupling method. Finite element method is used to establish the bridge model, and the vehicle is simulated as a multi-body dynamic model The mechanical characteristics of running tire are precisely modelled and the dynamic equations for the suspended monorail vehicle-bridge coupling system are derived. The proposed approach employs a double-line 7-span bridge with 210 m length as a numerical example, the impact performance of two track beams are studied and the results are verified by comparing with the theoretical solutions. The influences of critical system parameters, such as the train formation and double-line trains loads, on the dynamic responses of vehicles and the bridge are explored. The results show that it is feasible to study the impact effect with the proposed method. The separation phenomenon of rubber running tires jumping up on track surface occurs when vehicle speed is high, which may lead to negative impact coefficients. The impact coefficients of the track beam vary much with different locations, which can even be negative values at locations nearing the pier area. [ABSTRACT FROM AUTHOR]

Floating slab track is an effective countermeasure to mitigate undesirable vibrations caused by metro trains. In this work, a stochastic fractional derivative model is proposed for simulating the dynamic behavior of rubber bearings in floating slab tracks. The stochastic fractional derivative model is based on the Grünwald representation of fractional calculus, the number theoretical method, and the probability density evolution method (PDEM). It considers the viscoelastic characteristics of the rubber bearings, as well as randomness in mechanical behavior due to manufacturing tolerances, aging, and fatigue. The stochastic fractional derivative model is then implemented into a vehicle–floating slab track coupled dynamics model to investigate the vibration isolation performance of the floating slab track with rubber bearings. The characteristics and advantages of the stochastic fractional derivative model with deterministic parameters are illustrated by comparing the results with the conventional Kelvin model. Finally, stochastic analyses of the dynamic response and the vibration isolation performance of the floating slab track are carried out using the coupled vehicle–floating slab track system dynamics model. Results show that the stochastic simulation of the vehicle–floating slab track system using PDEM is efficient and reliable compared with the Monte Carlo method. Thus, the proposed model is effective and useful for evaluating the vibration levels in floating slab tracks with uncertain parameters, and for predicting the reliability of the vibration isolation performance. [ABSTRACT FROM AUTHOR]

The slabs of a floating slab track (FST) are usually discontinuously constructed, resulting in a gap between the consecutive slabs. Therefore, wheel/rail impact may occur when a train runs over the gap, resulting in an adverse effect on the train and track system. In this regards, the stiffness enhancement measure (SEM) is usually used at slab ends to enable a smooth stiffness change. The SEM normally includes installing end connections between consecutive slabs and increasing the supporting stiffness of slab ends. For estimating the influence of SEMs on dynamic behaviors of train and FST systems, a detailed and efficient coupled dynamic model of the train–FST system with the SEMs is first developed. Furthermore, the influences of the two SEMs on the system dynamic performance are revealed by using the proposed model. Finally, the optimal parameter combination of the two SEMs is determined, which provide a valuable guiding reference for the design of the FST. [ABSTRACT FROM AUTHOR]

• A new elastic side-supporting long sleeper damping track (ESSDT) is proposed. • A vibration reduction and frequency modulation device (VRFMD) is applied to the ESSDT. • The vehicle-track coupled dynamics analysis is achieved by co-simulation. • The VRFMD can adjust natural frequency and improve dynamics performance of the ESSDT. In urban rail transit, it is important to reduce the train-induced vibration on ambient environment. To achieve this goal, a new elastic side-supporting long sleeper damping track (ESSDT) is proposed in this study. Besides, a novel vibration reduction and frequency modulation device (VRFMD) is also proposed to improve the vibration damping performance as well as structural stability of ESSDT. Based on the vehicle-track coupled dynamics model and the finite element model of ESSDT, dynamic characteristics of ESSDT are investigated theoretically. The influence of key dynamic parameters of VRFMD on the damping effect and stability of the track system are studied in detail. Further, a hammer test was conducted on a full-scale test rig of ESSDT with VRFMD. Test results validate the theoretical research results, which proves that both the vibration of track and the vibration transmitted to the foundation can be attenuated effectively due to the installation of VRFMD. The results show that the spring stiffness of VRFMD has great influence on the dynamic response to ESSDT. The natural frequency of ESSDT could be adjusted by modifying the parameters of VRFMD, which may provide a new approach to avoid wheel-rail contact resonance. Moreover, VRFMD may also be introduced to other types of track for the purpose of vibration reduction and frequency adjustment, such as floating slab track and ladder sleeper track. [ABSTRACT FROM AUTHOR]