Horizontal dynamic forces generated by swaying and jumping

Modern assembly structures must be designed to withstand the dynamic forces generated by their human occupants; the characterization of these forces has become an important research topic. This paper focuses on the measurement and modelling of horizontal dynamic forces, which have previously received much less attention than vertical forces. Horizontal forces resulting from movements such as swaying and jumping were recorded using a tri-axial force plate and characterized using three properties: the impulse shape, the mean of the split impulse and the frequency spectrum. The fundamental force due to swaying occurred at the swaying frequency. However, the fundamental force due to jumping did not always occur at the jumping frequency, indicating that the current design procedure of assuming a horizontal load model similar to the vertical load model is not always appropriate. For some subjects the position of the centre of mass was simultaneously recorded using a motion capture system to establish a relationship between its velocity and the side-to-side force. Finally, a new, semi-empirical analytical model for representing horizontal forces in design calculations was developed. Results from the model show excellent agreement with measurements from the laboratory tests.