Study On The Tensile And Compressive Force Of Seamless Turnout On Bridge And Train-turnout-bridge System Spatial Vibration

Both seamless turnout and continuously welded rail (CWR) track onbridge are key techniques for high speed railway and heavy haul railwayto strengthen track structure. The mechanical mechanisms of bothseamless turnout and CWR track on bridge are very complex and theyhave always been the focal points and diffficulty points of railwaymodernization technique research. Because of the restriction of landformor environmental protection, seamless turnout will be unavoidably laid onbridge in newly-built railway or city elevated railway. The appearance ofseamless turnout on bridge leads to the appearances of two new researchdomains, which include research of additional longitudinal force anddisplacement of seamless turnout on bridge and research oftrain-turnout-bridge system dynamics. Because of the complexity ofseamless turnout on bridge, its mechanical mechanism is more complexthan that of seamless turnout on roadbed and of CWR track on bridge.Therefore seamless turnout on bridge will become another key techniquein the process of CWR track across station developing fast in China. Atthe present time, there is no engineering experience of seamless turnouton bridge in China, and the related theory research is also very few. Inorder to guide the future engineering practice with scientific theory, thispaper finished some pioneer theory researches as follows:(1) Aiming at ballast track, a finite element mechanics model wasestablished which can calculate the tensile and compressive force anddisplacement of seamless turnout (crossover) on bridge. In the model, theseamless turnout, beam, pier and abutment were considered as a system.The beam of bridge and rail was divided by bar element; turnout tie wasdivided by beam element; pier or abutment in fixed bearing wasconsidered as linear spring element; longitudinal ballast resistance,longitudinal fastener resistance, fastener torque, spacer pieces resistanceand spacing iron blocks were considered as nonlinear spring element. The nonlinear equation sets to solve the model were established by energyvariation principle and the "set-in-right-position" rule for formulatingmatrixes. Corresponding computer calculating programs weredeveloped with MATLAB.(2) The calculation model of tensile and compressive force anddisplacement of seamless turnout (crossover) on bridge was applied. Thedistribution rules of the tensile and compressive force and displacementof seamless turnout on simple-supported beam bridge, seamless turnouton continuous beam bridge, seamless turnout on continuous frame bridge,and crossover on continuous beam bridge were analyzed. The distributionrules of the tensile and compressive force and displacement of seamlessturnout on bridge, seamless turnout on roadbed and CWR track on bridgewere compared and the variation laws were studied. Some parametersinfluencing the tensile and compressive force and displacement ofseamless turnout on bridge were studied, such as the algebraic differencebetween rail temperature and the stress-free temperature, the maximumtemperature difference of beam, fastener resistance, ballast resistance, thegap of spacer, the rigidity of turnout tie, the location of spacer, the lengthof beam, the stiffness of pier and so on. The reasonable values ofparameters were suggested.(3) Aiming at ballast track, a track structure spatial vibration modelof multi-layer supporting system was established by using finite elementmethod. The rail-sleeper-roadbed spring-damping vibration model wasbuilt for section track on roadbed; the rail-turnout tie spring-dampingvibration model was built for turnout track on roadbed; therail-sleeper/turnout tie-bridge spring-damping vibration model was builtfor section track on bridge or turnout track on bridge. The vehicle spatialvibration equation sets, section track on roadbed spatial vibrationequation sets, section track on bridge spatial vibration equation sets,turnout track on roadbed spatial vibration equation sets and turnout trackon bridge spatial vibration equation sets were formulated by using the principle of total potential energy with stationary value in elastic systemdynamics and the "set-in-right-position" rule for formulating matrixes.The spatial vibration analysis programs of train-track system,train-track-bridge system, train-turnout system and train-turnout-bridgesystem were developed respectively with MATLAB. The availability ofmodels was testified by existing test results and research findings.(4) The train-turnout-bridge system spatial vibration model wasapplied. Taking TIAN-LUO major bridge in WENZHOU-FUZHOUrailway line for passenger as an example, it was assured that there was acrossover combined with two No.38 turnouts on the bridge. Thetrain-turnout-bridge system spatial vibration dynamic responses wereanalyzed when "China Star" high speed train with 1 locomotive and 4passenger cars at the speed of 200km/h through turnout main and at thespeed of 120km/h through turnout branch. The results were comparedwith those of train through turnout on roadbed and of train though CWRtrack on bridge. The variation laws of responses were studied.(5) Taking TIAN-LUO major bridge in WENZHOU-FUZHOUrailway line for passenger as an example, some parameters influencingtrain-turnout-bridge system spatial vibration were studied, such as trainrunning speed, rail supporting vertical stiffness, sleeper supportingvertical uniform stiffness, rail supporting lateral stiffness, sleepersupporting lateral uniform stiffness, the maximum value of verticalirregularity in turnout, the height of beam, the width of beam, the heightof pier and so on. The reasonable values of parameters were suggested.The research findings of this paper are important to guide the design,construction and maintaining of seamless turnout on bridge.