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The violent coupled vibration between the electromagnetically levitated vehicles and the steel switch girder had happened in several engineering practices, especially under the very low speed conditions. In order to simulate accurately the abnormal vibration and explore its underlying causes, this paper develops a distributed co-simulation framework, including maglev vehicle dynamic modelling by SIMPACK software, switch dynamic modelling by ANSYS software and a co-simulation coupler developed by C++ language to implement co-simulation of maglev vehicles and switch girder system. Dynamic response of maglev vehicles and switch girder system under various conditions of running speed and structural damping ratio are simulated and compared to obtain the mechanism and characteristics of coupled vibration. These results agree well with dynamic phenomena happened in the engineering practices. Further analysis shows that the levitation modules are impacted in turn by the vertical misalignments and rotation angles at both ends of switch girder, so that vibration energy of the switch girder cannot be attenuated rapidly by its relatively small damping and dead weight. The severe coupled vibration can be suppressed effectively by adding the tuned mass dampers, but improving constraints of switch girder and optimizing levitation control parameters should be paid more attention in the future. [ABSTRACT FROM AUTHOR]

With the ongoing development and deployment of medium-low speed maglev vehicles in China, it has become common to increase operational speeds from 100 km/h up to 140 km/h or even 160 km/h, necessitating further studies and simulation models to understand the implications of these changes. This paper analyzes medium-speed maglev vehicle-track-girder coupling dynamic performance at a speed of 160 km/h. First, a field dynamics experiment is carried out on the Changsha Maglev Express with a running speed of 80–140 km/h. Then we introduce the distributed coupling simulation platform for maglev transportation system (MTS-DCSP) and the vehicle-track-girder coupling model, taking into account the complex vehicle structure, the guideway structure, and the Proportion Integral Differential (PID) levitation control system. Together, this platform and model can conduct a simulation of the complete process at scale and at all degrees of freedom to obtain accurate results. Our analysis of the results gives an accurate portrayal of the coupling dynamics properties and validates the coupling model. The results from the field experiments together with the coupling simulation demonstrate that the medium-speed maglev train can operate safely and stably within the range of 140–160 km/h. While at 140 km/h, however, the Sperling ride quality index (RQI) is about 2.5, which is within the Excellent grade range, at a speed of 160 km/h, the Sperling ride quality index can increase to as high as 2.74, which is a grade of Good. Therefore, it is necessary to optimize the parameters of the secondary suspension system to improve the ride comfort of the maglev vehicle at 160 km/h. [ABSTRACT FROM AUTHOR]

To investigate the dynamic effects of bolster-hanger length on the 600 km/h high-speed EMS maglev vehicles, a dynamic model of three-car trainset is established, considering the kinematic relation of the bolster-hanger mechanism and the active levitation/guidance control system. Model validation is carried out by comparing simulated results with test results of Shanghai high-speed maglev vehicles. Then, the proposed model is used to simulate the dynamic response of maglev vehicles with four different hanger lengths of 0.12, 0.18, 0.24, 0.36 m and passing through the straight track, the horizontal curve and the vertical curve. Simulated results indicate that because of the too short hanger maglev vehicles cannot pass through safely the sharp horizontal curve, and deteriorate the lateral dynamic performance of maglev vehicles on the straight track. The too long hanger may increase the lateral displacement of the carbody and lateral forces of rubber stops of maglev vehicles on the large-radius horizontal curve. The hanger length has little influence on the dynamic response of maglev vehicle on the vertical curve. In sum, the medium-long (0.24 m) hanger can provide a stronger curve negotiation capacity and better ride quality of high-speed maglev vehicles. [ABSTRACT FROM AUTHOR]

This paper presents a multi-layer railway ballast track and substructure model, where a coupled discrete and continuous method is used for macro-meso dynamic behaviour analysis under moving wheel loads. In this coupled model, the discrete element method (DEM) is utilised to build the superstructure of the ballast track (i.e. rail, fastener, sleeper and ballast layer), which considers the complex ballast shape and particle size distribution from mesoscopic level. The finite difference method (FDM) is used to simulate the substructure (i.e. subgrade and foundation) with a consideration of computing cost. And then, the coupled model is achieved by satisfying displacement, velocity and contact force compatibility between the FLAC and the PFC. Finally, the dynamic analysis is carried out by applying the wheel-rail forces obtained from a vehicle-track dynamics model into the coupled model. The DEM parameters of ballast particles are calibrated based on the results of the ballast direct shear tests, and the dynamic behaviour of railway ballast track and subgrade system is validated with the field measurement. Through the numerical analysis, it is confirmed that the coupled DEM/FDM model can reliably reflect macro-meso dynamic behaviour and accurately reveal the contact characteristics between the ballast layer and subgrade. [ABSTRACT FROM AUTHOR]

The rail pad force and its stress distribution have critical influences on the performance and fatigue life of the rail, fasteners, and sleepers. The characteristics of the rail pad force and its stress distribution in the time and frequency domain obtained from field tests carried out using matrix-based tactile surface sensor are presented in this paper. The field testing involved rail pads under various axle-loads of running trains at different speeds. The influences that the train axle-load, the operational speed, and the rail pad stiffness have on the rail pad force and its stress distribution are analyzed. The test results indicate that the rail pad stiffness has a remarkable influence on the amplitude of the rail pad force but has little influence on its dominant frequencies. The first dominant frequency of the rail pad force is quite close to the passing frequency of the vehicle length. The stress distribution on the rail pad has a parabolic shape along the longitudinal and the lateral directions with the large stress appearing near the center of the rail pad, and is remarkably affected by the service condition of the rail pad. The maximum stress is about 2.5 to 3 times of the average stress, which is significantly greater than the nominal stress resulting from the assumption of uniform stress distribution. [ABSTRACT FROM AUTHOR]

This paper presents a full-scale laboratory test for investigating the track settlement and ballast degradation of the ballasted track–subgrade system on the high-speed railways. The test was carried out on a full-scale test platform with a ballasted track–subgrade system constructed exactly according to the construction standards of high-speed railways in China. In this test, four million cycles of cyclic loads simulating repeated high-speed train loads with an axle load of 140 kN were applied to the ballasted track–subgrade system through a specialized loading system. The vertical displacement and settlement of the rail, the sleepers and the subgrade at various sections and depths were recorded during the test. The test results show that the settlement of the high-speed railway ballasted track is very less. A logarithmic model was proposed for predicting the settlement of the high-speed railway ballasted track by fitting the measured data. Moreover, some painted ballast samples were embedded into the tested track to investigate the ballast degradation. After the test, it was found that more than 80% of the painted ballast grains remained intact and less than 20% were degraded. Four different ballast degradation phenomena were observed: corner or edge breakage, surface scratch, surface crack and the production of fine particles. The test results indicate that the high-speed railway ballasted tracks in China are very stable and the settlement is less under long-term cyclic loads, which could significantly benefit the track geometry and the railway maintenance work. [ABSTRACT FROM AUTHOR]