A Study On Vibration Test And Analyses Of A Special-shaped Footbridge Induced By Pedestrian

In the past decades years, with the continuous development of China’s economy and society, urban roads gradually developed to the three-dimensional, urban footbridges became an indispensable travel infrastructure. The improvement of Chinese urban public aesthetics, making the simply supported beam bridge does not meet the aesthetic needs of the people.In order to attract visitors, the scenic built a large number of beautfull footbridges. So while meeting the basic need of passage, handsome in appearance footbridge has become an important factor in the design process. Improvements of the design level, maturity of the construction technology, the developments of industrial technology, the development of new materials, making the development of the footbridge towards large-span, lightweight and flexible direction. In the pursuit of footbridge soft light, at the same time the main beam stiffness decreases, so that the main beam low-order natural frequency can be easily reduced in the range of the pedestrian’s walking frequency. When pedestrians cross the footbridge. The close of the pedestrians step frequency and the natural frequency of the main beam, causing the main beam more easily to intense vibration. That will cause light pedestrians discomfort, even seriously cause the footbridge crash making the social disasters.Current research on footbridge vibration can not give a clearly explanation. In many countries’ standard, the vertical natural frequency must be higher than pedestrian’s normal walking step frequency in order to avoid the pedestrians induced vibration of the footbridge. Some countries’ standard also limit the horizontal natural frequency to the guarantee the footbridge dynamic stability.This article describes the special-shaped footbridge development. Research of the pedestrian loading models. Some countries’ codes take the restrictive measures to control footbridge vibration. Footbridge vibration theory induced by pedestrians. This article bases on a footbridge of Guangzhou Science City to carry out the dynamic and Static tests and analysis. The difference between the natural vibration frequency of the footbridge and the updated footbridge ANSYS FEA model is less than 10%. The experiment of pedestrians crossing the footbridge contains these cases: a pedestrian crossing the footbridge with different speed, multi-pedestrian in row crossing the footbridge with a specific speed and multi-pedestrian in line crossing the footbridge with a specific speed. Comparing the FEA accelerate results with the footbridge test responses. The FEA calculate results are quite closed to the footbridge test responses. It shows that the response of the footbridge increase by the foot frequency. It also founds that, when the foot frequency goes faster than 3Hz, the vertical vibration of left span and right span goes opposite phase. The lateral vibration of left span and right span affect each other a lot. The quicker foot frequency is, the more obvious it becomes. The forced vibration frequency of the footbridge is closed to the excited frequency while the resonance is not occur.