Experimental Investigation on Synchronization of Bouncing Crowd

Abstract

Vibration problems concerning lightweight, flexible long-span floors and cantilever grandstands structures in engineering practice generally arise from crowd loading. Predicting the dynamic response of these structures due to crowd bouncing load has therefore become a critical aspect of structural vibration serviceability evaluation during live concerts or other large entertainments in public structures. This paper experimentally investigates synchronization of crowd bouncing. A crowd of approximately 50 persons participated in the experiment with each individual wearing three reflective markers on his/her clavicle. Verification experiments confirmed that the mean value of trajectories of the three markers can be employed to represent movement of center-of-mass of the person. Trajectories of all markers on all test participants were recorded simultaneously through a three-dimensional motion capture system consisting of 18 cameras. Various crowd densities and bouncing frequencies ranging from 1.5Hz to 3.5Hz with an interval of 0.1Hz were considered in the experiment. Moreover, various special test cases were conducted wherein each test participant was asked to wear an eye-patch avoid any visual influences. Preliminary analysis on the experimental data shows that for any of the fixed-frequency test cases the bouncing crowd can’t be perfectly synchronized. Each individual’s bouncing frequency in a crowd is found as following a normal distribution.