Study On Vehicle-Bridge Dynamic Responses With Flexible Carbody And Riding Comfort Evaluation

ABSTRACT:Nowadays, it has become a key part in the human-centered design of high speed railway to improve the riding comfort of moving vehicles. With the increase of train speeds, the dynamic interaction of train-bridge system becomes more significant in the high speed rail system. When a train travels over a railway bridge at high speeds, the bridge may produce quite large response and feedback it to the vehicles, which results in the deterioration of riding comfort of passengers obviously. Because of the development of railway vehicle design and manufacturing technology and the widely used of aluminum alloy profiled materials, the weight of the carbody decreases rapidly while satisfying the requirements of strength. But too light weight design of carbody is achieved usually at a cost of significant decrease in structural stiffness and cause the fiercely vibration of railway vehicles. So it is harmful not only to the dynamic responses of train-bridge system, but also to the riding comfort of passengers. In consequence, the refined analysis of train-bridge system model, the vibration of flexible carbody etc should be paid more attention, even if the interaction theory of train-bridge system dynamics becomes more and more perfect. In this dissertation, a train-bridge system dynamic model considering flexible carbody based on flex-rigid multibody system dynamics is established. Then the effects of bridge resonance, track irregularity excitation, flexible carbody resonance on the riding comfort of moving vehicles are studied, which is useful for the safety operation of high speed railway and the riding comfort of passengers. The main contents of the dissertation are listed as follows:(1) The riding comfort factors of moving vehicles and the correlation of riding comfort evaluation methods are analyzed. From the view of train-bridge coupling system, the riding comfort factors are investigated, including railway infrastructure vibration, track irregularity excitation, flexible carbody vibration, etc. Then, the riding comfort evaluation methods of moving vehicles are introduced, such as carbody acceleration index, Sperling index and ISO 2631 evaluation method. Based on the field test carbody acceleration data of China Railway High-Speed (CRH), the correlation of Sperling index and ISO 2631 comfort index is fitted with the least squares method.(2) The train-bridge system dynamic model considering flexible carbody is established and verified. In this study, the carbody is modeled as a simple uniform Euler-Bernoulli beam supported on secondary suspensions, and each of the two bogies and four wheelsets are regarded as rigid. A vertical vehicle rigid-flexible coupling system considering flexible carbody based on flex-rigid multibody system dynamics is established. Then with modal superposition method to determine the bridge deflection, the train-bridge system dynamic model considering flexible carbody is brought out. Finally, the train-bridge system program is executed and verified with theoretical and field test results.(3) The effects of bridge resonance on riding comfort of flexible carbody are studied. With the train-bridge system established in this dissertation, the dynamic responses of the train-bridge system are analyzed when the train travels over the simple supported bridge and two-span continuous bridge without track irregularity. The bridge resonance and sub-resonance are revealed, the suppression of bridge damping to bridge vibration, vehicle vibration and riding comfort of moving vehicles are analyzed. Finally, the effects of bridge resonance on riding comfort of moving vehicles are discussed.(4) The effects of harmonic excitation on riding comfort of flexible carbody are studied. Resonance mechanism of flexible carbody under harmonic excitation is analyzed and the cancellation condition of carbody vibration and the resonance condition of flexible carbody are proposed. Taking the harmonic irregularity as excitation source, the dynamic characteristics of train-bridge system are analyzed. Then the effects of bridge resonance, flexible carbody resonance on riding comfort of moving vehicles are discussed.(5) The effects of random excitation on riding comfort of flexible carbody are studied. Taking the random irregularity as excitation source, the dynamic characteristics of train-bridge system are discussed and the effects of random irregularity on flexible carbody vibration are analyzed. Then the effects of bridge resonance, flexible carbody resonance, the first vertical flexible frequency of carbody on riding comfort of moving vehicles are discussed.