Study On Human Induced Vibration And Vibration Control Of Pedestrian Bridge

In recent years,with the wide use of lightweight and high-strength materials,the continuous improvement of the structural design and construction level and the diversification of the functional requirements for pedestrian bridge,the development trend of pedestrian bridge is lightweight and large span,and the frequency of the structure also decreases.The resonance may occur when the frequency of the structure is close to or even falling into the frequency band of the load,which leads to comfort and even safety problems.Therefore,it is necessary to analyze the vibration of the pedestrian bridge in the design stage,and take vibration control measures when necessary.For the analysis of the vibration of the long-span and flexible structure,the reasonable representation of the human-structure interaction is an important part.However,due to the lack of deep understanding of the interaction,it is often ignored in the calculation of structural response,which affects the reliability of the calculation results.In addition,most of the studies on the tuned mass damper(TMD)in the field of human induced vibration control of long-span bridges are numerical simulations,while the manufacturing accuracy and installation will influence the damping effect,even cause it can not work.Therefore,it is urgent to carry out field experiments to analyze the effect of TMD system and its influencing factors.In view of the above problems,this paper takes the large span pedestrian bridge as the research object,and the main work is as follows:(1)Based on the self-exciting human model,the motion equation of footbridge was established with considering the vertical human-structure interaction and the walk force model was proposed with considering main harmonic and sub-harmonic frequency of walking.Based on relevant experiments,the analysis of the effect of sub harmonic frequency on the structural response was carried out.The influence factors of human-structure interaction are also analyzed.(2)The equations of motion for the vertical coupling system of human-bridge-TMD are established and it is verified by experiments.Based on this,the influence of the technical parameters and structural performance on the damping effect of TMD is analyzed.(3)After the modal identification of the experimental pedestrian bridge,the vibration reduction design is carried out.Performance evaluation of the TMD products is also carried out.On this basis,the structural response test with or without TMD was carried out on the experimental pedestrian bridge,and the damping effect of TMD is evaluated according to the test.The main conclusions are as follows:(1)The sub-harmonic component of walking frequency is more obvious when human walking on light and low damping structures.And the result indicates that walking sub-harmonic frequency may be close to the fundamental frequency of structures,resulting in large structural response.Therefore,in the design of structure,consideration should be given to the sub-harmonic component,and avoid it close to the basic frequency of structure resulting in excessive vibration.(2)The natural frequency of structures and human/structure mass ratio have a great influence on human-structure interaction.When the structure frequency is similar to walking frequency and main harmonic components,the coupling effect is significant.Moreover,with the increasing of human/structure mass ratio,the interaction will strengthen gradually.(3)For light and low damping structures,the damping effect of TMD is closely related with human walking frequency.When the sub-harmonic is close to the fundamental frequency of the structure,it will lead to a large structural response,and the response component is dominated by the first order modal.At this time,the TMD system designed for this mode has played a good role in vibration control.