Study On Alignment Parameter And Its Vehicle Dynamic Behavior For High-speed Railways

It is crucial for the railway industry to increase the speed of the train to keep its market share and gain more profit in the modern society, and building high-speed railway is the trend of the railway construction today. However, the track-train interaction changes greatly with the increasing of the speed under the same track condition. The vertical and lateral acceleration of the carbody and the attenuation distance of the car vibration are increased, and with a higher possibility of various vibrations to overlap with each other. The train running safety and passenger comfort are more sensitive to the track condition. The performance of the high-speed train and the structure of the track have been enhanced in order to decrease the negative impact on the track and train caused by the increased speed and to keep the geometry of the track more easily. The route alignment is vital to train running safety and passenger comfort, and it is also a key factor to affect the cost of the railway project. In order to enrich the highspeed design theory and engineering practice, it is of great significance to make further study on the alignment parameters. Thus route alignment is a hot topic in the research of railways around the world today and many researchers are studying it. There are many parameters that affect the performance of the alignment. Many theoretical studies and field tests on the parameters have been made in the past few years.This paper analyzes and summarizes the former studies on the parameters, and makes a further study on it by means of theoretical analyses, field test and numerical simulation. The major work and outcomes of the study are as follows:1. The alignment parameters of existing high-speed railways around the world are summarized, with the focus put on the theories and types of the transition curve. A general design method for the transition curve's algebraic equation is presented, by which different transition curve equations under different transition modes condition could be obtained.2. The equations of lateral change of carbody acceleration and the change rate, of carbody roll angular velocity are deduced, considering the acceleration and deceleration" of the train. In order to simplify the calculation, the train is considered as a mass point according to the kinematics theory. The train is assumed to running on the track smoothly and the wheel-rail contact closely all the time. The train's behaviors under different operating states are studied by means of theoretical calculation. Different types of transition curves of the route are considered for each operating state. The results demonstrate that the suggested equations of the lateral change of carbody acceleration and the change rate of carbody roll angular velocity, which takes into consideration the acceleration and the deceleration of the train's speed, could be used for the selection of the different type of the transition curve. Theoretically, the higher-degree transition curve is better than the cubic parabola transition curve in terms of passenger comfort.3. A high-speed train-track dynamic simulation is made through the combination of the commercial software and programmes compiled by us. The UM software is selected after comparing it with several other famous rolling stock dynamic analyzing softwares. The high-speed vehicle dynamic model is developed by the UM software, while the model of the track is developed on the MATLAB platform through programs compiled by us. The wheel-rail contact model is created on the basis of the vehicle model and track model through calculation.4. Both field test and simulation by software of the vehicle's behavior are conducted in the route section of the transition curve and vertical overlapping plane circle curve in order to get the following index:the wheel/rail vertical force, wheel/rail lateral force, derailment coefficient, and reduction rate of wheel load. The results indicate that the difference between the two group data respectively obtained from the field test and simulation is minor. They have the same pattern though there are some differences in the values. Two purposes are achieved through the field test: one is to verify the validity of the alignment parameters, and the other is to evaluate the accuracy of the simulation.5. The alignment of the route section where the plane curve and vertical curve overlap is considered as a space curve. The space geometry parameters and physics characters of the curve are analyzed according to the kinematics and space geometry. The behavior of the vehicle running on this overlapping section under different operating states is studied in order to develop the theoretical equation of each aforementioned evaluative index of the vehicle when it runs on this section. The impact imposed on train running safety and passenger comfort by the overlapping of the plane curve and vertical curve are studied, both by theoretical analyses and simulation. The results indicate that the start point and the end point of vertical curve always excert more negative effects on train running safety and passenger comfort. More negative effects are imposed on train running safety and passenger comfort if the overlapping is made up by a convex vertical curve and a plane circle curve, compared with that made up by a convex vertical curve and a plane transition curve. Relatively speaking, the overlapping of a concave vertical curve and a plane curve could improve train running safety and passenger comfort to some extent. Therefore, different types of overlapping should be treated differently when we design the route. Different suggestions should be made for different conditions of overlapping when we work out the high-speed railway route alignment standard.6. A comprehensive study on the high-speed railway route alignment parameters is made, and their effects imposed on the train-track interaction are presented. The following evaluative index are studied by establishing the high-speed railway train-track dynamic simulation model:the lateral acceleration and its change rate of the carbody, the vertical acceleration of the carbody, the wheel-rail vertical force, the wheel-rail lateral force, the derailment coefficient, and the reduction rate of wheel load. Based on the study of the aforementioned indexes, the law of the effect imposed on the train-track dynamic response by the alignment parameters are extracted, including the type and length of the transition curve, superelevation, curve radius, length of intermediate straight line and intermediate circular curve, length of the vertical curve and grade section, distance between vertical curve and transition curve, as well as the overlapping of plane curve and vertical curve. In addition, the sensitivity of the high-speed train dynamic response to the value and the form of the track geometry deviation is discussed.