Sensitivity analysis of coupled crowd-structure system dynamics to walking crowd properties

Increasing vibration serviceability problems of modern structures have drawn researchers' attention to the walking-induced vibration modelling and assessment of floors and footbridges. Changes of dynamic properties of structure due to presence of stationary people have been studied extensively in the literature. However, little is known about the similar effects of walking people, mainly due to the lack of experimental evidence and credible models capable of simulating human-structure dynamic interaction (HSI) in the vertical direction. This paper uses a single degree of freedom mass-spring-damper (MSD) model to simulate dynamics of walking crowd on structure and investigates the sensitivity of the coupled crowd-structure system frequency and damping to properties of crowd model. Results of this study show that when the natural frequency of the crowd model is less than the natural frequency of the structure, both natural frequency and damping ratio of occupied structure are more sensitive to crowd's model stiffness. Similarly, when the natural frequency of the crowd model is greater than the natural frequency of the structure, both natural frequency and damping ratio of occupied structure are more sensitive to crowd's model mass. It also can be seen that natural frequency of theoccupied structure has no sensitivity to damping of the crowd model while its damping ratio shows a limited sensitivity to the crowd's model damping with the maximum where both natural frequencies are equal.