EFFECT ON MODAL PROPERTIES OF A SIMPLY SUPPORTED EULER BEAM OCCUPIED BY A DISTRIBUTED CROWD

This paper studies effects of modal properties of a simply supported Euler beam occupied by a uniformly distributed crowd. The crowd is modeled as uniformly distributed mass- spring-damper system or mass- spring system. Both these two models are studied to investigate the influence of the occupied crowd on the modal properties of the beam. Analytical solutions of the natural frequencies and damping ratio of the crowd-beam system are obtained. The mass ratio of the crowd to the beam is taken as a key parameter, whose effect on the natural frequencies and the damping ratios of the crowd-beam interaction system is studied, and qualitative conclusions are reached on how the crowd affects the properties of the beam. Results demonstrate the branching a bound of natural frequencies of the crowd-beam interaction system from the natural frequency of the human body; when the mass ratio of the crowd to the beam is large enough, the dynamic characters of the beam are changed greatly, and the damping ratio of the coupling system is increased significantly as well. At the end of this paper, the effect of the natural frequency of the beam on the damping ratio of the coupling system is investigated.