Computational Theory And Vibration Analysis Of VBI Problem For Long Span Suspension Bridges

As the important infrastructure, bridge is the important subject investigated of the vibration reduction and disaster resistance. Since the long span suspension bridges play an important role, the dynamic characteristics of the coupling interaction between vehicle and bridge is an important research subject needs to pay more attention.Recently, with the development of the world economy and technical advancement, the high speed railway becomes the most economic and the most efficiency transport system in the world. With the increasing of the running speed of the vehicles, the VBI problem (the coupling interaction problem between the vehicles and bridges) becomes more serious. In the past, great deal research on the VBI problem was conducted and many solution methods were provided. But most of the solution methods are very complicated and don't have versatility for various bridge types. So it has great significance to develop a program, which has good versatility and high precision.In this dissertation, considering the shortage of the other methods, the VBI problem of the long span suspension bridges under moving vehicles was studied based on the summary of general study of the predecessor's research experience in China and abroad in this field. A method was provided to deal with the VBI problem, and detailed calculating methods were provided to calculate the static characteristics and determine the target configurations under dead loads for the long span suspension bridges. The main research work is as follows:1. The static calculation problem of long span suspension bridges was discussed. In this dissertation, the static calculation method of suspension bridges based on the deflection theory was derived. The second order nonlinear term of the live load was considered in this paper, and the validity was verified. Finally, the comparative study of stiffening girders continuous or hinged at the pylons under temperature load was made.2. The refined nonlinear finite element method was provided to determine the target configurations under dead loads for the long span suspension bridges. In this dissertation, several analytic methods of determining the target configurations were reviewed firstly, and then nonlinear finite element method based on the nonlinear catenary cable element were derived. The detailed calculating procedure was provided. In this paper, several classical examples were adopted to verify the validity of this method, and the target configuration of a suspension bridge crossing the Changjiang River was studied.3. The classical VBI theories for simply supported beam were reviewed. The analytic calculation methods were reviewed for simply supported beam under moving force, moving mass, moving single axle vehicle and moving double axle vehicle.4. Detailed research on modeling the vehicle and the bridge was made. Firstly, the fundamental elements of vehicles were introduced. Especially, the method dealing with the rigid connections was illuminated. And the modeling method for arbitrary complex vehicle was provided. The dynamic models were built for double axle vehicle and four-axis vehicle. The method building the dynamic model of long span suspension bridges was also introduced.5. The simulation method for road roughness was provided based on the stochastic theory. In this dissertation, several common power spectral density expressions for road roughness were introduced, and the simulation method was provided based on the harmonic superposition. The method to determine the range of spatial frequency, the sampling period and the sampling time step was introduced. At last, simulation was made for several common grade of road pavement, and the power spectrum estimation was compared with the theoretical power spectrum.6. The VBI element was derived, and a method calculating the VBI characteristics was built. The VBI element subjected to moving general vehicles was derived. The method of establishing the VBI equations and solution procedure were detailed introduced. In this dissertation, the influence matrices of VBI element under moving mass, moving single axle vehicle, moving double axle vehicle and moving four-axis vehicle. At last, the validity of this method was verified, and the dynamic response of a suspension bridge crossing the Changjiang River under moving trailer vehicle and train was solved.7. A method of solving VBI problem under seismic action was provided. In this dissertation, the vibration differential equations of the VBI problem were derived, and the VBI problem of a suspension bridge crossing the Changjiang River under seismic action was studied.