Human-induced vibration of a bridge and its mechanism

点击翻译按钮获取中文摘要

Observation of human-induced large-amplitude lateral vibration of an actual pedestrian bridge in an extremely congested condition is reported. Walking motions of pedestrians recorded by a video camera are analyzed. It is found that walking among 20% or more of the pedestrians was synchronized to the girder lateral vibration. With this synchronization, the total lateral force from the pedestrians to the girder is evidently increased and it acts as a resonant force on the girder lateral vibration.An experiment on human walking is carried out using laterally shaking floor in order to clarify causes of pedestrian-induced lateral vibration observed in an actual bridge. The purpose of the experiment is to make clear the changes of characteristics of walking under the lateral motion of the floor. Lateral motion of the neck of the human body is measured by an acceleration meter, while the lateral force exerted by walking is measured by pressure meters. Synchronization of human walking to the floor motion is confirmed and it is found that the lateral motion during walking increases as the amplitude of the floor shaking increases. According to these experimental results, it is pointed out that lateral vibration of a bridge occurs through synchronization of human walking to the floor.Pedestrian-induced lateral vibration of a bridge is studied using a two-legs rigid rocking model for human walking. Lateral force exerted by walking is calculated by this model and is found to agree with the experimental data. A bridge where lateral vibration is observed is chosen as a case study. Interaction between human walking and the girder is studied using the model under the assumption that there is a phase lag between human motion and walking force. The calculated amplitude of the girder is as the same order as of that bridge. According to these results, the mechanism of pedestrian-induced vibration is also discussed as an interaction of human and girder.