Structural Behavior Analysis Of Long Span Railway Suspension Bridge During Train Braking Process

In the vast territory of China, it is inevitably to stride great rivers and grand canyons in the process of railway construction. In some great rivers, it needs to build the railway suspension bridge to meet the navigation requirements. In some special grand canyons, arch bridge can’t meet the span requirement; the side span of cable-stayed bridge is too short; it’s better to consider the suspension bridge to ensure the construction safety and to achieve a more reasonable structure system. It’s inevitably to meet the case of braking while trains are moving on the bridge. But most works investigate the bridge responses under the moving vehicle with uniform vehicle speed. For the railway suspension bridge with strong nonlinearity, it needs to further study the transmission mode of the braking force and the structural responses excited by the vehicle brake. The main research contents, methods and contributions are as follows:A three dimensional computer model of railway suspension bridge was generated using a commercial general finite element analysis software ANSYS. Combined with the track structure parameters, an improved model of track-bridge system was generated. With the simplified train load loaded on the track-bridge model, the transmission mode of the braking force was studied with different initial train positions at braking.Three kinds of suspension bridge structures were established, which were the longitudinal constraint system, the semi floating system and the damping system. Opening the large deformation function of ANSYS, static responses of the structures under the braking force were studied by considering the moving train with a constant speed and train braking on the bridge.Establishing the loading mode of the braking forces varying with time, dynamic responses of the three structure systems were analyzed during the braking process. At the moment the train stops, the braking force quickly drops to 0, which causes an impact effect on the bridge. Using the transient analysis function of ANSYS, the dynamic responses of main components of the structures were analyzed under the impact effect.The calculation results show that the additional flexural force has very little effect on the railway suspension bridge and can be ignored. Under the braking force, the displacement and the velocity of the beam end of the semi floating system are far greater than the other two systems; braking force has little effect on the tower top displacement for the three systems; internal forces of tower bottom of the semi floating system are the smallest in three systems, those of the longitudinal constraint system are the largest; by installing viscous dampers, the tower bottom shear is 1.53 times of that of the semi floating system,46.5％ of that of the longitudinal constraint system, the tower bottom moment is 1.13 times of that of the semi floating system,71.9％ of that of the longitudinal constraint system. Under the impact effect after the completion of brake, attenuation vibration periods of the displacement and the velocity of the beam end of the semi floating system are long, the beam end of the longitudinal constraint system has a slight vibration and the amplitude is small, the damping system effectively restrains the response of the beam end; the internal forces of the tower bottom of the longitudinal constraint system are deeply affected by the impact effect that internal forces fluctuate within a large range, while the other two systems have no such phenomenon. Under the effect of train braking force, the semi floating system and the longitudinal constraint system have their own advantages and disadvantages, the damper system can fully exert the advantages of the first two systems, and avoid their disadvantages when choosing the proper damping parameters.