Wind-Vibration Response Analysis Of Steel Truss Suspension Bridge

With the continuous development of bridge girder wind engineering and construction technology,the span of steel truss suspension bridge is increasing day by day,the structure is more gentle,and it is more sensitive to the average wind action.As the main load-carrying component of suspension bridge,the sling has relatively small stiffness,mass and damping,which is especially easy to vibrate under various excitations,resulting in the identification accuracy of its damping ratio is not high all the time The wind-induced vibration analysis brings a lot of trouble,especially for the research on the influence of the change of sling damping ratio on the buffeting response of suspension bridge is a little insufficient.In order to explore the mechanism of sling vibration,the following research is carried out to study the influence of sling damping ratio and vortex induced vibration effect on the buffeting of suspension bridge.Firstly,the finite element analysis is carried out for an engineering example,and the buffeting response analysis foundation of suspension bridge is established by Davenport buffeting theory,and the dynamic characteristics of sling are analyzed.Then,the single sling girder damping model and sling stiffness model are established,and the free vibration attenuation method is used to calculate and analyze the sling damping.Finally,the influence of the length,initial tension,diameter and wind speed of the sling on the buffeting response of the suspension bridge is analyzed1)The results of numerical simulation are feasible,and the response of suspension bridge buffeting mainly depends on the lower frequency,while the higher frequency has little influence on the buffeting response;2)With the increase of the length,diameter and wind speed of the suspension bridge,the displacement and lateral displacement of the mid span and L / 4 span of the suspension bridge will increase,but the influence of the length on the vertical bending has no obvious trend;3)With the increase of the initial tension of the sling,the lateral displacement of the mid span and L / 4 span of the suspension bridge decreases,and the vertical bending displacement also decreases;4)The buffeting displacement is 32.6% larger when the damping ratio is not considered when the wind speed is 20 m / s.with the increase of wind speed,the influence of the damping ratio is more obvious,and the mean square deviation of lateral and vertical buffeting of suspension bridge is larger when the damping ratio is not considered.In addition,this paper also analyzes the fluid structure coupling effect of the sling,and simulates the fluid structure coupling effect of the sling by the method of ANSYS and CFX processing,analyzes the vortex induced vibration of the sling by FLUENT software,and analyzes the amplitude of the fluid structure coupling effect of a single sling and the coupling effect of the vortex induced vibration of the string double slings on the amplitude of the sling vibration.According to the results:1)The results of single sling numerical simulation verify that the calculation of sling stiffness and damping ratio proposed in this paper is more consistent with the real situation of sling vibration,and the upstream and downstream slings will affect each other under a certain spacing ratio;2)With the change of sling stiffness and damping ratio,the non-factor amplitude of sling also fluctuates.When the sling stiffness decreases,the non-factor amplitude increases slowly,and when the sling damping ratio increases,the non-factor amplitude of sling decreases;3)When the distance ratio of the upstream and downstream slings of the suspension bridge is 4,the wake generated by vortex induced vibration of the upstream slings will have a great impact on the downstream slings,so the distance ratio of the slings of the suspension bridge should be controlled above 5.