Vibration-Prone Structures: Uncertain Effects of Human–Structure Interaction on Ground Reaction Forces and the Cadence of Walking Individuals

This study addresses the vertical human–structure interaction (vHSI) and its effect on vertical ground reaction forces (vGRFs) as well as on gait adaptation in terms of cadence adjustment by analyzing the gait of individual subjects crossing an experimental pedestrian bridge. A comprehensive study was performed on 26 subjects to compare GRFs of two structural configurations. In the single-span configuration, the structure is susceptible to human-induced vibrations, while in the second system configuration, the bridge can be regarded as rigid ground, making it ideal for studying the influence of vHSI. The results show a positive correlation between increasing bridge acceleration and increasing peak vGRF values. Furthermore, subjects with a preferred cadence in the range of the structure’s natural frequency tend to synchronize with it. Although the effect of vHSI on gait adaptation and the change in vGRFs is clearly shown, this work also demonstrates a high uncertainty of vHSI effects due to inter- and intravariability. The results emphasize the need for further studies on active HSI effects on human gait to base structural load modeling on more valid assumptions.