Human damping and its capacity to control floor vibrations

This paper addresses a damping mechanism not often considered although typically present. The damping mechanism in question is that originating from stationary humans (standing or sitting) on floors. Floors may encounter vertical vibrations due to actions of humans in motion. The vibrations hereby generated can be a problem because stationary humans are excellent vibration sensors and may perceive vibrations as being discomforting. This paper demonstrates that in addition to acting as receivers/perceivers, stationary humans can also add significant damping to the floor which they occupy; and thus assist in reducing the discomforting vibrations. In the analyses the stationary crowd of people are modelled as an auxiliary (spring-mass-damper) system attached to the floor. Experimental results reported in this paper show that this modelling approach is reasonable even though a rigid mass assumption is often used. The latter model does not account for a human damping mechanism. Implications of its presence are evaluated for a set of floors. These evaluations also encompass the scenario that a tuned mass damper (TMD) is fitted to the floor so as to mitigate excessive floor resonant vibrations. The effectiveness of such TMD is shown to reduce substantially during the presence of stationary humans on the floor.