Study On Dynamic Interaction Of Tram Train-Embedded Rail Track

Tramway transportation experienced a history of rising, declination, and reviving. It has the advantages of wide applicability and high construction flexibility, which can meet different needs from variety of passengers, cities, and regions. In China,72 cities from 25 provinces are planning to build more than 50 tram lines with total planning mileage more than 1300 km and total investment more than 300 billion RMB. However, the construction of modern tramways just starts developing in China, the standards and the research related to the construction and operation of tramways are very limited. To support the rapid development of modern tramways in China, theoretical and experimental researches on the tramway system are urgently needed. The study on dynamics of tram vehicle-embedded rail track system is very important from the theoretical and engineering practice points of view. The main research work in the present dissertation includes:(1) The history and current status of studies on the dynamics tramway system are reviewed. The significances and research directions of tram train-embedded rail track system dynamics are indicated.(2) A tram train-embedded rail track interaction model is established on the basis of the multi-body dynamics approach and the finite element method. In the model, the tram train is modeled as a system with 96 degrees of freedom and nonlinear suspensions. The inter-vehicle joints are modeled using kinetic constraint approach, and the inter-vehicle dampers are modeled as nonlinear damping elements. The embedded rail track model consists of two continuously elastically supported Timoshenko beams as the rails, a three-dimensional solid finite element model for the slabs. In the slab model, continuous viscoelastic elements are used to represent the filling material and the elastic subgrade. The concrete support beneath the slab is simplified as effective springs and dampers. The effect of basement is not considered. A nonlinear wheel/rail contact model is used to couple the vehicle subsystem with the track subsystem, the geometric relationship between the wheel and the rail is solved using the wheel/rail contact point trace method and the minimum vertical distances approach. The wheel/rail normal force is calculated using the Hertzian nonlinear contact model, and the creep force calculation employs Shen’s model. The reliability and the accuracy of the established model are then validated through a detailed comparison between the simulation results and the field test results.(3) The standards and criteria that could be used to estimate the dynamic behaviors of tram vehicles and tracks are summarized. The vibration tests of a tram train operating on an embedded rail track are introduced and the related test results are discussed. The behavior of tram train-embedded rail track is then analyzed through the numerical simulations.(4) The proposed tram train-embedded rail track interaction model is used to investigate the dynamic behaviors of the tram train-embedded rail track system under the excitation of the track irregularities with various wavelengths and amplitudes. The characteristics of the track irregularities include two aspects:the sensitive wavelengths and the allowable safety amplitudes. The analysis results show that the sensitive wavelengths of the embedded rail track irregularities for the running safety and ride comfort are in the wavelength from 1 to 20 m and from 1 to 40 m, respectively. And the allowable safety amplitudes of the alignment, gauge, longitudinal level, cross level, and twist of track irregularities are suggested with respect to the running safety and ride comfort of tram train. These results help to support the rapid construction of modern tramways and to establish the irregularity control standards for the embedded rail track in China.(5) To investigate the effects of wheel/rail abnormal wear on the tram train-embedded rail track interaction, three typical types of wheel/rail wear patterns, including the wheel flat, rail weld and rail corrugation, are considered. A series of numerical investigations using the dynamic model of tram train-embedded rail track interaction are carried out to describe the effect of the wheel flat, rail weld, rail corrugation on the dynamic behaviors of the tram train-embedded rail track coupling system. Based on the numerical simulations, three remedies to mitigate the negative effects of the wheel flat, rail weld and rail corrugation are suggested and discussed.(6) The tram train-embedded rail track interaction model is used to investigate the effects of physic parameters of the embedded rail track on the dynamic behaviors of the tram train-embedded rail track system. Based on the dynamic performances of the tram train, the track parameters, including the stiffness and damping of the filling material, the dimension of concrete slab, and the stiffness and damping of the elastic subgrade beneath the concrete slabs, are optimized. At last, some preferred ranges of the parameters of the embedded rail track are suggested, which will be helpful for the design of new embedded rail tracks and support the construction of modern tramways in China.