Dynamic Performance Analysis Of Suspended Monorail Train-bridge System Under Earthquake

With the rapid increase of urban population in China,urban ground transportation is facing tremendous pressure,and vigorously developing urban rail transportation has become an inevitable choice for metropolises.In the existing urban rail transit systems,the suspended monorail system has a broad application prospect in China because of its unique running mechanism and many advantages.China is located between the Asia-Europe plate and the Pacific plate and the earthquake has a wide range of seismicity,large strength and high frequency in China.When the earthquake occurs,the dynamic interaction of the suspended monorail train and bridge will significantly increase,and it may lead to a strong vibration of the suspended monorail system,even causing bridge damage.This may seriously threaten the safety of people ’s lives.Therefore,studying the coupling vibration response of the suspended monorail train and bridge system under earthquakes has important theoretical significance and engineering application value for the aseismic design of the suspended monorail system and the guarantee of traffic safety in China.Firstly,the development history of suspended monorail is introduced,and the advantages and development prospects of suspended monorail system are also analyzed in this thesis.Simultaneously,the researches about the coupled vibration analysis of suspended monorail train and bridge under earthquake condition are summarized and organized at home and abroad.The coupled dynamic model of suspended monorail train and bridge is established based on finite element theory and vehicle-bridge coupling dynamics theory.At the same time,based on the suspended monorail test line in Chengdu,the experiment study on vehicle-bridge coupling dynamic performance was carried out.Then,the vibration accelerations at the middle of span,the top of pier and vehicle obtain by numerical simulation are compared with the test data.The results show that the simulation results are in good agreement with the measured results,validating the effectiveness of the established dynamic model.Then,utilizing the established coupled vehicle-bridge dynamic model and applying the earthquake load by using the large-mass method to constrain the foundation of the bridge finite model,the dynamic performances of the vehicle and bridge subsystems are investigated and subsequently the effects of earthquake type,earthquake intensity and train speed on the vehicle-bridge dynamic response are also revealed.The results show that different earthquake types will cause the large discrepancies in the waveforms of the vibration acceleration curves of the suspended monorail train-bridge system,however the maximum acceleration under these earthquake types are relatively close.When the train speed is the same,the earthquake intensity has a significant influence on the vibration of the bridge,however,the earthquake intensity has a little effect on the vibration of vehicle.When the earthquake intensity is larger than 0.2 g,the mid-span displacement of track beam would be large,and the vehicle vibration would be also violent,which should be paid some attention in safety issues of system operation.When the earthquake intensity is the same,the train speed has a great effect on the vibration response of the vehicle,however it has a little effect on the lateral vibration response of the pier.Finally,the effects of the structural parameters of suspended monorail track beam and pier on the dynamic performance of the suspended monorail train-bridge system are studied under earthquake.The results show that the thickness of steel plate on running surface of track beam has a small effect on the vibration acceleration of the suspended monorail trainbridge system,but it has a great effect on the deformation.When the design basic seismic acceleration is 0.2 g,it is recommended that the design thickness of steel plate on running surface of track beam be 36 mm.The height of the pier has a great effect on the lateral vibration response of the suspended monorail bridge,and the vehicle vibration acceleration is relatively smaller affected by the pier height.Therefore,under the prerequisite of meeting the requirements of building limits and clearance requirements,the height of pier should be reduced as much as possible or the section size of pier should be increased appropriately.