Study On Dynamic Analysis And Design Methods Of The Turnout Layout Geometry

The horizontal alignment selection in turnout design is one of decisive factors to affect the speed by train passing over a turnout and the using performance. It is necessary to choose appropriate plane alignment for turnouts of various numbers and different application ranges to satisfy the train running safety and stability, and structural stationarity. Based on the existing theories in our country and abroad, the selection and evaluation and design method for turnout horizontal alignment were studied in this paper. The main content is divided into the following five aspects:1. wheel/rail contact geometry calculation method established according to various horizontal alignments for turnoutsBased on the typical wheel/rail contact geometry calculation method for common track rail, the turnout wheel/rail contact relationship calculation method was set up. The detail steps are listed:firstly apply cubic spline function to fit rail profiles in the key sections in turnout zone, and obtain profiles in any calculation section by interpolation between key sections; secondly use contact line method to get a space curve of all possible contact points on wheels; finally use minimum distance method to find out the wheel/rail contact point between the calculation section and the space curve, and then calculate all responding contact parameters. Following the steps above, the subprogram to calculate the wheel/rail contact geometry in turnout zone was developed. This subprogram can not only be applied into evaluating the influences of turnout horizontal alignment to wheel/rail contact relationship, but also was a key part to make the upper vehicle and lower switch structure form a coupling relationship which was essential in the dynamic program.2. Vehicle-turnout dynamic coupling model establishing and solutionBased on vehicle dynamics and turnout dynamics, vehicle-turnout dynamic coupling model was established to analyze the influences of horizontal alignment to the system vibration characteristics. The vehicle sub model was a single vehicle multi-rigid body model which was composed of the car body、two bogie and four wheelsets. In this model, the car body and the two bogie were both modeled with consideration of the five degrees of freedom including floating-sinking, sway, rolling, galloping and hunting; the wheelsets were modeled with consideration of four degrees of freedom including floating-sinking, sway, rolling and hunting; all rigid bodies were connected by the spring-damping component. Turnout sub model was built up with consideration of the three main structures including switch, common crossing and closure rail, and also of other components, and then all components were dispersed into finite element model. Apply the wheel/turnout contact relationship to couple the twp sub models, use Hamiltonian theory to establish the whole system equation, and then develop the calculation program for vehicle-turnout dynamic coupling model, and finally guide the turnout horizontal alignment design from the dynamic perspective. 3. Vibration characteristics analysis of vehicle-turnout dynamic coupling model with various horizontal alignmentsDifferent analysis cases were designed according to the parameters and the types of various horizontal alignments. The vibration characteristics of all cases were comparatively analyzed by using vehicle-turnout dynamic coupling model, and the influences of the speed by train passing over turnout to the system dynamic responses were also analyzed. Results show that small-size turnouts with single circular or composite circular alignment and large-size turnouts with circular-easement or easement-circular-easement curves can both satisfy the safety and stability when trains pass through turnout branch at their permissive speed, and the turnout structure stability; increasing curve radius of turnout branch or choosing small-size turnouts with composite circular alignment and large-size turnouts with easement-circular-easement curve can improve train running performance and turnout adaptability by train passing over it. However, the specific alignment should be determined with the overall consideration of structure dimensions、designs and working conditions.4. The influences of the cutting style of switch rail to the system dynamic responses and rail wearing ability in switch zoneBased on vehicle-turnout space coupling vibration model and wear index calculation method, the system vibration responses and rail wearing ability of various sizes turnouts with the switch rail of different cutting styles were comparatively analyzed, and the influence of the speed by train passing over turnout and alignment parameters’ changing to the wear index was also analyzed. Results show that when the cutting way of small-size turnout switch rail is semi-tangent or semi-secant alignment, the vehicle running state and rail wearing ability are good, and changes little with the change of the train passing speed and the radius of turnout branch. When the cutting way is disjoint semi-tangent, all respects of states are decreased, but this cutting style significantly improves the robustness of switch rail, so it can also be one of the cutting styles of switch rail; large-size turnout with semi-tangent switch rail can make the running state be best, and rail wear index less, so its applicability is best.5. The establishing of the calculation method applied to various turnout horizontal alignmentsThe plane parameter method was set up which could carry out the calculation of various turnout horizontal alignments; the key parameters of four horizontal alignments including single circular、composite circular circular-easement and easement-circular-easement, and of five switch rail cutting styles including tangent, semi-tangent, secant, semi-secant, and disjoint semi-tangent were derived, and all types of turnouts were evaluated in terms of structure dimension and kinematics. Three kinds of switch sleeper layout were introduced, which were the straight-line layout, the sector layout and a layout being vertical to the crossing angle in the crossing zone. All the switch sleeper layout methods can reduce error caused by human factors, and lay the foundation for turnout horizontal alignment design.6. The development and confirmation of the calculation and drawing software of turnout horizontal alignmentBased on the plane parameter method, the calculation and drawing software of turnout horizontal alignment was developed. This software consisted of the calculation module and the drawing module. By setting the original parameters, it could provide lots of design plans with different combinations of four horizontal alignments、five switch-rail cutting ways and three switch-sleeper layouts, and then it drew all alignments to provide for the plan comparison and selection. This software improved the efficiency of turnout alignment design. Different horizontal alignments for low-speed small-size turnout and high-speed large-size turnout were calculated respectively by using the software, and the results verify the usability of the software.