Influence of the random dynamic parameters of the human body on the dynamic characteristics of the coupled system of structure–crowd

Abstract

The presence of human occupants may change the dynamic behaviour of structures considerably. While this effect is considered in mechanical engineering (e.g. interaction between driver seat and driver) and biomechanics (potentially damaging effects of vibrations) by using equivalent mass–spring–damper systems for the human body, the design practice in civil engineering still often clings to the so-called mass-only model, i.e. the occupants are considered only as additional masses when analysing the dynamic behaviour of floor slabs and stand structures. Recent research efforts aim to improve this situation by recommending averaged models for the human body. This approach seems to be reasonable for large crowds; however, for smaller groups, the question arises whether the random scatter in the dynamic characteristics of the human body leads to random scatter in the effective natural frequency and the effective damping of the coupled structure–crowd system. Based on a probabilistic model for the dynamic characteristics of the human body, an extensive study is presented in this paper. The key variables are the natural frequency of the bare structure, the ratio of the crowd’s mass to the structure mass and the group size. The scatter in the effective dynamic characteristics of the coupled system is revealed by the 90%-confidence interval. Furthermore, the maximum span of the respective bounds is used to identify cases where the averaged model fails to predict the real behaviour of the coupled system.