Analysis of time-varying dynamic characteristic parameters of footbridge and TMD vibration control

Dynamic characteristics of footbridge are the main factors that affect the comfort level of pedestrian on the bridge. Based on the influence of random crowd walking on modal damping ratio and modal frequency of pedestrian bridge, considering the active and passive gait adjustment strategy of human-human interaction, a stochastic crowd concentration model dependent on the pedestrian synchronization rate was established. The coupling dynamic equation of random crowd-footbridge-TMD system was deduced. The time-varying law of dynamic characteristic parameters of footbridge was analyzed. The TMD vibration control design method based on time-varying dynamic characteristic parameters of footbridge was proposed. The results show that the first instantaneous damping ratio of the footbridge increases greatly with the increase of the crowd density under random crowd walking when the human-human interaction is considered, and the increment is positively correlated with the fundamental frequency and modal quality of the footbridge. The first instantaneous frequency of the footbridge decreases continuously with the increase of the crowd density under random crowd walking, and the decrement is negatively correlated with the fundamental frequency of the pedestrian bridge. The time-varying dynamic characteristic parameters of the footbridge based on vibration control design method can effectively reduce the vertical vibration response of single person walking at fixed frequency, single person randomly walking and random crowd walking. Under the case of 0.6 person/m2 random crowd walking, the reduction rate of vertical footbridge vibration acceleration reaches 72%. © 2020, Editorial Office of Journal of Building Structures. All right reserved.