Study On Vibration Effect Of New Prefabricated And Assembled Pedestrian Cable-stayed Bridge Under Crowd Load

With the use of new bridge structure,construction splicing method and highstrength and light-weight materials,pedestrian overpasses are developing towards the direction of flexible and long-span,which leads to the decrease of vibration frequency of the structure,falling into the range of pedestrian-sensitive step frequency,resulting in the resonance phenomenon of the structure under pedestrian load,and the pedestrian discomfort when the vibration response exceeds the threshold that the human body can withstand.Therefore,in the design stage of footbridge,it is necessary to focus on the comfort of pedestrians.Based on the cable-stayed pedestrian bridge of Aolin Plaza in Nanjing,the vibration response and comfort evaluation of the structure under humaninduced excitation are studied and analyzed by combining the measured results with the finite element analysis.Firstly,this paper reviews the origin of the famous pedestrian-induced vibration events and pedestrian bridge vibration problems,and introduces the current research status of pedestrian bridge vibration problems at home and abroad,including the following four aspects: pedestrian foot dynamic load research,mainly the introduction of experimental platform and experimental methods;pedestrian parameters research,mainly the statistics of pedestrian stride frequency in various countries;the study of comfort mainly focuses on the sensitivity of pedestrians to vibration,and the study of pedestrian-induced vibration control of pedestrian bridges mainly introduces the vibration-absorbing devices of structures.Secondly,by consulting relevant literature at home and abroad,the basic principle of pedestrian bridge vibration and pedestrian load model are sorted out.Through the comparison and analysis of load models and comfort limit values of BS5400 code in Britain,EN1990 code in Europe,Bro2004 code in Sweden,ISO code in International Organization for Standardization and EN03 code in Germany,the research methods and index selection in this paper are determined.Thirdly,using the finite element software Midas,the dynamic characteristics of the cable-stayed pedestrian bridge in Aolin Plaza,Nanjing are analyzed to obtain the dynamic characteristics of the structure.The influence of assembly joints on the vibration characteristics of the structure is simulated by equivalent spring connection,and the accuracy of the finite element model is verified by field measurement.Then,according to the loading modes proposed in the national codes listed in this paper,the vibration response of the background bridge under pedestrian load is simulated by using the dynamic time history analysis module of Midas software,and the comfort evaluation is carried out by combining the comfort index proposed by the codes.In addition,the different responses obtained under different loading modes of the codes are compared.Finally,the effects of concrete modulus of elasticity,cable-stayed bridge structure system and cable area on structural vibration characteristics are analyzed and compared.Under the same load frequency,the response difference of the structure when the basic frequency avoids or falls into the sensitive step frequency range is compared.In view of the situation that the vibration response of the structure exceeds the norm limit under a certain working condition,a single tuned mass damper(TMD)and multiple tuned mass dampers(MTMD)are applied to analyze the vibration reduction effect and reasonable application mode of the device,which can provide reference for the design of bridge vibration comfort.