Random field model for crowd jumping loads

Abstract

A reliable model for crowd jumping loads is a prerequisite to an accurate prediction of a long-span structure’s response when subjected to crowd motion triggered by music and other mass appeal events. Because of the lack of crowd jumping experimental data, crowd jumping load models are scarce with few data available on this type of synchronisation among people. Inspired by the random field model of earthquake excitations, this study attempts to develop a random field model for crowd jumping loads based on extensive records from unique crowd jumping load experiments. A framework for the random field model of crowd jumping is first proposed, in which auto-power spectral density (PSD) and cross-PSD functions of individual and group jumping loads are defined. The auto-PSD was obtained by updating a model in a previous study. Experiments were conducted on a jumping group of 48 persons using a 3D motion capture technology. A cross-PSD model for any two persons in a jumping group was then developed based on the experimental data. Having obtained a PSD matrix for crowd jumping, the structural response could then be predicted by the stochastic vibration theory. Finally, the feasibility of the model was verified by comparing the measured responses of an existing floor with the prediction responses using the proposed model.