Research On Human-induced Vibration Of Bridge Based On Air Damped TMD

Today,in bridge structure construction,due to the requirements of landscape design and the application of high strength lightweight materials,the progress of footbridge tends to be long span,gentle and low damping,which leads to the frequent occurrence of large vibration events caused by pedestrian load and the discomfort of pedestrians crossing the bridge.Tuned mass damper(TMD)is a passive control technology in vibration control of structures.Owing to its excellent vibration reduction effect,simple structure and low cost,TMD has been widely used in pedestrian bridge vibration control.General TMD is much sensitive to frequency,once frequency imbalance occurs,the damping capacity of TMD will be rapidly reduced.The damping force of air damped can remain stable for a long time,the production cost is low and the later maintenance is less.In this paper,air damper is applied to TMD,Maxwell model of viscous damping is introduced into the calculation model,the vibration reduction effect of air damped TMD and TMD is compared.An air damped TMD used for vertical vibration control is designed and applied to the vibration reduction experiment of footbridge.The main contents are as follows:(1)In this paper,the TMD control model and air damped TMD control model of single degree of freedom structure under harmonic excitation are established respectively.The dynamic amplification coefficient based on displacement control is derived by using the motion equation,and the fixed-point theory for optimal parameter design of dampers is introduced.According to fixed-point theory,the method of finding optimal parameters of TMD and air damped TMD is explained.The text has analyzed the effect of mass ratio of damper,and compared the damping performance of TMD and air damped TMD under the same mass ratio.The results show that air damped TMD has better damping effect and wider damping frequency band.(2)Taking simply supported beams as research objects,the motion equations of bridges subjected to pedestrian load under uncontrolled,TMD controlled and air damped TMD controlled are established.Based on the code,assumption is made about the pedestrian load.On the basis of the parameters of a simply supported beam bridge,the model of simply supported beam bridge is established in Ansys and the result of finite element analysis of structural first frequency is basically consistent with the theoretical value,then the module composition and simulation analysis are found in MATLAB/Simulink.In this article,taking peak acceleration as the carrier,the influence of external excitation frequency and mass ratio on the damping effect of air damped TMD has been analyzed,and completed the comparison of damping effect between air damped TMD and TMD from the point of view of bridge vibration control.The results show that air damped TMD is insensitive to the change of external excitation frequency,and the damping effect is better than TMD under the same conditions.(3)This paper introduces the design principle of air damping,devises an air damped TMD for vertical vibration control,and applies it to human induced vibration control of a simple beam footbridge and carries out experimental research.Taking the peak acceleration as an index to evaluate the vibration comfort,the influence of different walking modes on the vibration response of bridges is discussed.For air damped TMD,the influences of mass ratio,installation position and pedestrian step frequency on damping performance of the damper are analyzed.The experimental results show that the air damped TMD designed in this paper can significantly reduce the vibration response of the simply supported girder bridge under pedestrian excitation,and the influence of various factors on the damping effect of air damped TMD is basically consistent with the conclusion of the simulation.