Study On The Vehicle-bridge Coupled Vibration Of The Long-span Double-deck Cable-stayed Bridge With Pedestrian Bridge Of "S" Shape

With the maturity of bridge calculation theory and the application ofhigh-strengthen material in bridge engineering, the bridge structure tends to be lighterand more flexible, for instance, the development of suspension bridge and long-spancable-stayed bridge. On the other hand, with the rapid development of economy andgreat demanding of fast and convenient transportation, the load and speed of vehiclesare increasing. It is obvious that the proportion of the load of vehicles in the total loadof bridge is continuously growing. Thus, the dynamic response of bridge is prominentbecause of the load of vehicles. All the factors show that the effect of vehicle-bridgecoupled vibration should be paid much attention.In this paper, the writer brings forward combination equation to solve thevehicle-bridge coupled vibration based on the previous research achievements. Inaddition, on the basis of the engineering background, Lounge No.1Bridge in Mianyang,the following research findings are respectively studied:Oscillatory differential equation of vehicles is deduced according to theD’Alembert theory. On the basis of structure finite element theory, both the finiteelement model and the vibration differential equation of bridge structure are alsoobtained. What’s more, to build the model of vehicle-bridge coupled vibration, thewriter couples the vehicle and bridge through the displacement compatibility conditionsof wheels and bridge deck according to the assumption of close contact.The writer has studied the traditional iterative solution and applied VB.ENTprogramming language to program the calculation program of iteration aboutvehicle-bridge coupled vibration. As the iteration method, however, is a method ofseparate iteration, its calculation efficiency is low. The integral solution method,constraint equation analysis method, is studied on the basis of Ansys constraint equationin this paper. Then the calculating program of constraint equation about thevehicle-bridge coupled vibration is programmed with the APDL programming languageto develop Ansys for the second time. The research reveals that there still exist somedefects to deal with the problems of structural damping in Ansys constraint equationanalysis method. They have great influence on the results of damping vibration. In order to solve the problems of structural damping, on the basis of integral solution of Ansysconstraint equation method, the writer proposes combined equation analysis method tosolve the two vibration differential equations of vehicles and bridge combined. And acalculation program of iteration method about vehicles-bridge coupling vibration isprogrammed with Matlab. All have proved the feasibility and validity of combinedequation method.According to the practical engineering situations of bridge deck pavement, thewriter has done simulations of the irregular bridge deck. Then the function oftime-domain samples about the unsmooth bridge deck is obtained. The research revealsthat whether the bridge floor is smooth has greater influence to the vibration of vehicles,but less to bridge.④According to load of I level in JTG D60-2004and load of truck-over20in JTGD60-1989, the writer applies the equivalent principle of bridge mid span’s verticaldisplacement, and uses the inverse method to obtain the correspondent types of vehicles,axle load, distance, and number of vehicles. The certain distribution of traffic stream isaccordingly obtained.For the practical case, the writer has done the analysis and calculation ofvehicle-bridge coupled vibration with the above theories. And the vibration response ofvehicles and bridge is obtained when certain traffic flow across the bridge. Finally, thewriter also analyzes several significant factors of vehicle-bridge coupling vibration thatcould affect the practical engineering.