Influence of uncertainties on dynamic properties and responses of human-structure coupled system under bouncing excitations

The consideration of inherent uncertainties of the human-structure coupled system during serviceability assessment has become a consensus in recent years. The uncertainties from human body and structures are coupled and propagate together through the human-structure interaction (HSI) effect. However, how each random source affects the system output under rhythmic motion remains unclear and lacks investigation. In this paper, a method for uncertainty quantification and global sensitivity analysis for large-span floors under crowd bouncing is introduced. Both the uncertainties from the structure and the human body are considered through an HSI analytical model. The Kullback-Leibler (K -L) divergence indices and probability density evolution method (PDEM) are adopted for the uncertainty analysis. Dynamic properties and vibration responses of four structures with different characteristics are investigated. Parametric analysis of structural modal mass, damping ratio, and natural frequency is carried out for general insights and a quick method identifying the important variables is proposed. The influence on dynamic reliability after eliminating unimportant variables is investigated. It is found that a bouncing crowd has limited influence on structural frequency regardless of the structural characteristics but may significantly increase the structural damping ratio and its variability. The human body damping ratio and the human body frequency are the main influential parameters for the structural damping ratio in most cases. The structural acceleration responses under crowd bouncing are with large variability, which needs to be considered during the calculation. The mass, frequency, damping ratio of human body, the mass, and the damping ratio of structure are unimportant for acceleration responses in most cases, while the frequency of bouncing activity and structure are important in most cases. The importance of biomechanical load factors heavily depends on the structural frequency and the structural damping ratio. The reliability results only considering the suggested important variables are accurate enough for the engineering practice.