Experimental And Theoretical Study On Vertically Coupled Vibration Between Human And Bridge

In recent years,with the widespread application of high-strength materials and the huge advances in civil engineering construction technology,footbridges have developed more soft.The natural frequency and damping ratio of the footbridge are lower.The vertical interaction between human and structure is more prominent,and the problem of human induced vibration serviceability is becoming more and more prominent.However,the vertical interaction between human and footbridge obtained by different researchers is quite different,and the main influencing factors are not clear.In addition,existing research often focuses on the study of standing occupants-bridge or pedestrian-bridge coupling vibration.However,the footbridge such as landscape bridges often has both standing occupants and pedestrians,and human-bridge coupling vibration is more complicated.Related theoretical analysis methods and vibration comfort evaluation indexes also need to be improved.In this paper,the effects of standing occupants and pedestrian on the dynamic characteristics and the response of the human-structure interaction system were investigated through experimental research and theoretical analysis,based on the model of simply supported steel structure glass footbridge made by the research group.Results of this paper and typical literatures are compared and summarized.The vertical coupled vibration of pedestrian-footbridge-TMD(tuned mass damper)is analyzed by numerical simulation.The main conclusions of this study are summarized as follows:(1)The variation of the modal mass ratio is an important reason for the fluctuation of the effect of standing occupants on the first vertical modal frequency and damping ratio of the footbridge,which takes into account the number and position of standing occupants.With the increase of the modal mass ratio between standing occupants and bridge,the first vertical modal frequency of the footbridge decreases linearly,while the first modal damping ratio of the footbridge increases gradually and then tends to be stable.(2)By comparing the theoretical and experimental results of the dynamic characteristics and dynamic response of the standing occupants-bridge and pedestrian-bridge coupling system,the selection of human body load model is suggested.The M-SD model of a standing occupant load and the A-MSD model of single pedestrian load are more accurate,applicable and stable.It is preferred for the detailed analysis of human-bridge coupled vibration.(3)The vertical coupling vibration test of standing occupants-single pedestrian-simple supported beam bridge shows that the acceleration of the footbridge in the standing occupant residence is generally less than the actual acceleration of the standing occupant.This paper proposes a theoretical analysis method for standing occupants-single pedestrian-bridge coupling vibration,and the responses of footbridges and susceptors can be accuratelypredicted.(4)This paper proposes a refined analysis method for calculating the dynamic response of a footbridge with TMD.This method can be applied to the fine assessment of vibration comfort of a footbridge with TMD.When the pedestrian on the footbridge is low density distribution,the interaction between human and bridge is not prominent.Predictive analysis of coupled vibration response can ignore human-bridge interaction.While when the pedestrian on the footbridge is high density distribution,the interaction between human and bridge is more significant.Predictive analysis of coupled vibration response must consider human-bridge interaction.