Effects Of Pedestrian On Wind Resistance Performance Of Long-span Flexible Footbridge

With the wide application of new lightweight materials in bridge,long-span flexible footbridge has become more important in the field of footbridge construction in China.Because of the low stiffness and small damping,the long-span flexible footbridge is more sensitive to wind load.Wind-induced vibration of bridge will affect the safety and comfort of pedestrians,and even cause fatigue damage or collapse of bridge.In addition,with the increasing urbanization rate,the burden on footbridges is increasing.Most footbridges are built in the high altitude of the city or in the scenic spots of mountains.On the one hand,they face complex wind environment,on the other hand,the existence of pedestrians on the bridge is bound to affect the wind resistance performance of the bridge.However,the research on the influence of pedestrian on the wind resistance performance of footbridge is almost blank.Thus,it is necessary to study the influence of pedestrians on the wind resistance performance of long-span flexible footbridge.This paper firstly reviews the development of footbridge and wind resistance,and summarizes the basic theory of bridge wind resistance.Secondly,in order to study the influence of pedestrian on the wind resistance of long-span flexible footbridge,taking a footbridge in Xiamen as the engineering background.Then analyze the static and dynamic characteristics of this bridge by finite element simulation.Finally,to systematically study the variation of tri-component coefficients and vortex vibration performance of long-span flexible footbridge under different pedestrian density and pedestrian position by wind tunnel test.The specific research work is as follows:(1)Combined with the material properties and characteristics of footbridge components,a finite element model of footbridge is built by using ANSYS software.The internal force and the displacement response of the main girder under the static wind load are analyzed.The results show that the influence of static wind load on the main girder can negligible.(2)Based on the established three-dimensional finite element model,the modal analysis of the footbridge is analyzed,and the natural characteristics of the structure are obtained,which offers data foundation for the production of wind tunnel test model.Then,pedestrian is regarded as a point attached to the bridge deck,which forms a pedestrian-bridge system with the footbridge.Taking the weight of pedestrian as the main variable parameter,the inherent characteristics of pedestrian-bridge system are studied.The results show that the increase of weight has little effect on the inherent characteristics of pedestrian-bridge system,so it is not necessary to consider the weight of pedestrian in the follow-up wind tunnel test research.(3)Based on the finite element analysis,the characteristics of footbridge are obtained.The pedestrian density and lateral arrangement of pedestrian are taken as the influencing factors of tri-component coefficients of girder section,through the combination of wind tunnel test and CFD method,the tri-component coefficients of the main girder with different inlet angles on both sides were studied.The results show that pedestrian density is the dominant factor in the range of negative wind attack angle,and the wind attack angle is the dominant factor in the range of positive wind attack angle.The results suggest that the pedestrian density on the bridge should not exceed 0.5 person/m2.(4)Through the theoretical analysis and experimental research in the previous study,the vortex vibration performance of the main girder is analyzed by wind tunnel test.According to the results of modal analysis and similarity criteria,the test model is made,and the vortex vibration performance of the main girder is analyzed through wind tunnel test.The influence of wind attack angle,pedestrian density and pedestrian transverse arrangement position on the vortex vibration performance of the main girder is mainly studied.The research work of this paper provides the relevant experimental basis for the study of pedestrian impact on the wind resistance of footbridge,which is conducive to the following researchers to continue this research.