Vibration Analysis Of Vehicle-bridge Coupling Of Long-span Self-anchored Suspension Bridge

Large-span self-anchored suspension bridges have a flexible structural system and are susceptible to large vibrations under vehicle loads,making the issue of coupled vehicle-bridge vibration a hot topic in bridge engineering research.In the current research results on the coupled vibration of large span self-anchored suspension bridges,the influence of the mass shear eccentricity of the main girder section and the initial strain of the tower girder on the dynamic response of the bridge is seldom considered.Therefore,based on the existing research results,this paper takes a large-span selfanchored suspension bridge as the research object,uses ANSYS to establish its finite element model,converts the bridge model data into data files of existing analysis programs,carries out its bridge vibration analysis,and explores the influence of different factors on the dynamic response of the bridge coupling system.The main research contents are.(1)Coupled vibration analysis method and program design for highway bridgesAccording to the coupled vibration theory of road and bridge,the vehicle-bridge coupling system is divided into two subsystems: the bridge adopts the conventional finite element method to form its equations of motion,and the vehicle is modelled as a multi-rigid body system with interconnected springs and damping elements,to establish a spatial three-axis vehicle model and derive its equations of motion.Considering the roughness of the road surface,the vehicle and bridge equations of motion are coupled by means of the displacement coordination condition and the force balance condition at the contact points of the vehicle and bridge,and the dynamic response of the vehicle and bridge is obtained by the separation iteration method.Based on the above theory,the analysis process of the coupled vibration of a highway bridge is presented in conjunction with the existing programming.The reliability of the axle coupled vibration analysis procedure is verified by conducting experiments on the axle coupled vibration model of highway bridges.(2)Finite element modeling and self-vibration characteristics analysis of largespan self-anchored suspension bridgesThe three-dimensional finite element model of a large-span self-anchored suspension bridge is established using the finite element software ANSYS,and the selfweight droop of the main cable is corrected by adjusting the modulus of elasticity of the material through the Ernst formula;the stress stiffening effect is used to add the additional stress stiffness matrix to the main stiffness matrix in the analysis process,and the initial internal force effect of the main cable,boom and tower beam is considered in this way.Initial strains are applied to the main girder,main tower,main cable and boom according to the bridge alignment.The bridge self-vibration characteristics are analyzed to summarize the characteristics of the vibration patterns of large-span self-anchored suspension bridges.The results show that the beam vibration patterns of large-span self-anchored suspension bridges are dense and the first-order vibration pattern is longitudinal drift,and the longitudinal restraint stiffness of the bridge is small;the vertical vibration pattern of the structure plays a dominant role in the structural dynamics.(3)Analysis of the factors influencing the coupled vibration of large span selfanchored suspension bridgesThe ANSYS model data of the large-span self-anchored suspension bridge is converted into the data file of the existing analysis program,and the coupled vibration analysis of the bridge is carried out to explore the influence of parameters such as mass shear eccentricity of the main girder section,initial strain of the tower girder,traffic speed,main cable stiffness and random traffic flow on the dynamic response of the bridge,and to evaluate the driving comfort according to the vehicle dynamic response evaluation criteria.The results show that: 1)the mass shear eccentricity(vertical)of the main girder section mainly affects the lateral dynamic response of the bridge,and as the lane moves out,the more detrimental it is to the lateral dynamic response of the bridge.2)the initial strain applied to the beam only has a greater effect on the bridge displacement response,and the initial strain applied to the tower girder has a greater effect on the bridge acceleration response.3)the increase in traffic speed will aggravate the vibration response of the bridge.4)the increase in the stiffness of the main cable makes the bridge vertical displacement decreases and lateral displacement increases;the acceleration response of the bridge structure is greater at 1.00 times the stiffness of the main cable.5)The effect of traffic with higher weight in the middle on the dynamic response of the main girder,main cable and boom is more obvious,and the effect of traffic with higher weight in the front on the dynamic response of the top of the tower is greater.