|Title:||Dynamic analysis and alignment design of high-speed maglev trains running on straight, circular and transitional viaducts|
|Advisors:||Xu, You-lin (CEE)|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Magnetic levitation vehicles
High speed trains
Bridges -- Live loads
|Department:||Department of Civil and Environmental Engineering|
|Pages:||xxi, 9, 214 pages : color illustrations|
|Abstract:||In the past two decades, magnetic levitation (maglev) train, a high-efficiency intercity transportation, has attracted the world's attention for its advantages over conventional wheel train systems, such as higher speed, lower risk of derailment, and less energy consumption. Thus far, several maglev train lines, such as the Shanghai Maglev Line (SML), the Changsha Maglev Express, and the Incheon Airport Maglev, have been built in urban areas. The maximum operating speed of the SMLis 430 km/h, and the design speed of the Chuo Shinkansen Line (under construction) reaches 500 km/h. In view of the limited space available in urban areas, maglev trains often run on elevated viaducts supported by slender piers. Thus, the dynamic interaction between high-speed maglev trains and viaducts becomes significant and plays a crucial role in the design of the vehicles in the train and the major components of the viaduct. Furthermore, curved tracks/viaducts are inevitable in maglev lines because ofland use compatibility in urban areas. Therefore, accurate dynamic analysis and alignment design of high-speed maglev trains running on straight, circular, and transitional viaducts are extremely significant for the safety and comfortability of maglev trains, the safety and functionality of the viaducts, and the construction cost reduction. This thesis first presents a realistic and detailed high-speed maglev train-viaduct interaction model. It focuses on the accurate simulation of the two subsystems, namely, the train subsystem, including the magnets, and the viaduct subsystem, including the modular function units of the rails. The electromagnet force-air gap model with a proportional-derivative controller is adopted to simulate the interaction between the maglev train via its electromagnets and the viaduct via its modular function units. The flexibility of the rails, girders, piers, and associated elastic bearings are considered in the modeling of the viaduct subsystem to investigate their effects on the interaction between the two subsystems. By applying the proposed model to the SML, the effectiveness and accuracy of the proposed approach are validated through the comparison of the computed dynamic responses and frequencies with the measurement data. This thesis confirms that the proposed model with detailed simulation of the magnets and modular function units can duly account for the dynamic interaction between the train and viaduct subsystems. Maglev lines are often built in the urban areas; thus, horizontally curved tracks are inevitable because of land use compatibility and socioeconomic consideration, and circular curved tracks are often introduced for this purpose. However, due to high speed of maglev trains, a large cant angle is often required to avoid the use of a large curve radius (CR) 0and at the same timeto counteract the circular curved path-induced centrifugal forces onthe vehicle. Accordingly,the issues of curving ride quality of the train and safety performance of the viaduct increase with high train speeds. However, when a vehicle moves on the curved track, the moving direction of the vehicle in the global coordinate system changes. As a result, the direction ofthe centrifugal force on the vehicle also changes. Meanwhile, the interaction forces between the vehicle and track depend on their relative displacements. The dynamic interaction between the high-speed maglev train and the slender curved viaduct becomes extremely complicated. This thesis proposes a trajectory coordinate-based framework for the analysis of the high-speed maglev train running on the circular curved track. The motion of the maglev train system running on a curved track is defined by a series of trajectory coordinates, and the stiffness and damping matrices of the equations can be reduced into those of the straight track. The curved viaduct system is modeled in the global coordinate system using the finite element method. The electromagnet force-air gap model is also adopted for the maglev vehicle via its electromagnets and rails on the viaduct by appropriate transformation of coordinates. By applying the proposed framework to the SML, curved path-induced dynamic characteristics and responses of the vehicle are explored, which agree well with the measured ones. Moreover, the results of parametric studies show that the track radii and cant deficiencies significantly affect the operational safety and comfortability of the viaduct.|
To ensure the ride quality of the train moving from the straight track section to the circular curved track section, a transitional curved track section imbedded between themis also necessary. However,as required by the geometric smoothness of the entire track, the CR and high difference (HD) between the outer and inner rails along the transitional curved track are distance-varying, resulting in a more complicated dynamic interaction than one when trains run on either the straight track or the circular curved track. Thus, the proposed trajectory coordinate-based analysis approach is extended and further developed, in which the origins of the trajectory coordinate systems move along the inner rail of the track, and the Euler angles used to describe the coordinates' orientations are functions of distance-varying CR and HD. By applying this framework to the SML, the dynamic characteristics and responses of the maglev vehicles running on the transitional viaduct are numerically explored, which match the measured data quite well. Moreover, the effect of transitional track length and cant deficiencies on the coupled system are investigated. Results show that the rolling motions of the vehicle are considerable and affect ridequality when the vehicle runs on the transitional track with a high cant angle. Cant deficiency and transitional length significantly affect the vehicle-viaduct interaction. From a practical perspective, the reduction of construction cost is consistently pursued in the alignment design of a high-speed maglev line. Optimizing the alignment parameters of the curved track is crucial in providing an economical but reliable solution for the construction of new maglev lines because the construction of acurved track is considerably more expensive than a straight track, and the ride comfort is markedly more serious. Hence, a new optimization method is proposed in this thesis for the alignment design of horizontally curved track in a high-speed maglev line, in which the minimum length of the curved track is a major objective function, and the satisfaction of the minimum comfort level of passengers is a boundary condition to constrain the selection of alignment parameters of the curved track. By comparing with the existing solution and the actual curved track ofthe SML, the solution provided by the proposed optimization method is proven an optimal solution with the minimum length of the curved track and the satisfactory comfort level. The accuracy of the optimal solution provided by the proposed optimization method is further validated by using the coupled maglev train and curved viaduct system established in this thesis. Results demonstrate that with the increase of the vehicle speed, both the radius of the circular track and the length of the transitional track increase. However, the cant remains constant at its upper limit value andthecant deficiency varies slightly around a constant value. The optimal solution provided can be used for the initial alignment design of horizontally curved track in a high-speed maglev line.
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