The Analysis Of Vehicle-bridge Coupling Vibration Of CFST

With the development of the construction of CFST,the vehicle safety and vehicle comfort are being regarded more and more during the normal operation process of CFST.Therefore,carrying out the analysis of vehicle-bridge coupling vibration of the large span CFST arch bridge has important theoretical significance and engineering value.Maocaojie Bridge in Yiyang city of Hunan Province was taken as the engineering background,three-dimensional finite element analysis model of the two-way four lane three span self-anchored CFST tied arch bridge was built.Meanwhile,the vehicle was simulated as a three axle model with 9 DOFs.The contact surface between the wheels and bridge was taken as boundary,and the vehicle and bridge were established as two subsystems.Vibration differential equations of vehicle and bridge were established respectively.The two subsystems were coupled by concordance of displacement and equilibrium of force to be a total vibration differential equation.an the platform of numerical analysis software named ANSYS,Newmark-β method was used to compile command stream.Random traffic flow was simulated by MATLAB with normal distribution function.Four kinds of bridge deck roughness samples with different roughness were simulated by trigonometric series method.The roughness samples were taken as vibration excitation to compute vehicle-bridge coupling vibration under different conditions which including road roughness,velocity,transverse brace,boom section area,the structure damping ratio.The influences of different working conditions and factors on the dynamic responses of the bridge and the vehicle were obtained,and the regularities were determined.The various factors influencing the response of vehicle-bridge coupling vibration were analyzed.Some useful conclusions can be used as a reference for arch bridge design and study on the coupling vibration of vehicle and bridge.(1)With the situation of bridge deck pavement irregularity becoming worse,the peak of vertical vibration displacement and acceleration at midpoint of main span increase nonlinearly;the peak of vibration displacement and acceleration of the vehicle increase;the peak of impact coefficient increases nonlinearly.Therefore,the the dynamic responses of the bridge and the vehicle are influenced significantly by the roughness of pavement surface.(2)With the increase of vehicle speed,the peak of vertical vibration displacement and acceleration at midpoint of main span increase;the peak of vibration displacement and acceleration of the vehicle increase;the peak of impact coefficient increases first,and then decreases from 35 m/s.Therefore,the the dynamic responses of the bridge and the vehicle are influenced significantly by vehicle speed.(3)The arrangement of the transverse brace in the arch bridge has little influence on the response of vehicle-bridge coupling vibration,and its main function is to improve the lateral stiffness and wind resistance of the structure.(4)With the increase of cross section area of hanger rod,the peak of vertical vibration displacement decreases nonlinearly,while the peak of vertical vibration acceleration increases first,and then decreases;the peak of vibration displacement of the vehicle changes very little;the impact coefficient of the normal stress in the midspan of bridge girder decreases first and then increases,and the minimum value is obtained at 1 times of the boom section area.Therefore,the purpose of reducing the impact coefficient can not be achieved by simply increasing the cross sectional area of the suspender.Instead,it is necessary to find an optimum cross sectional area to minimize the impact.(5)With the increase of the structure damping ratio,the peak of vertical vibration displacement and acceleration at midpoint of main span decrease nonlinearly;the peak of vibration vertical displacement of the vehicle increase nonlinearly;the peak of impact coefficient increases nonlinearly.Therefore,damping ratio is also an important factor affecting the dynamic response of bridge structure.