Modelling crowd-structure interaction on an ultra-lightweight FRP footbridge

Abstract

Human-Structure Interaction (HSI) may influence the dynamic behaviour of Fibre Reinforced Polymer (FRP) footbridges due to the lightweight nature of composite materials. Hence, load models that account for HSI should be applied to accurately predict vibration levels on these pedestrian structures. This paper proposes a model to assess the structural response of a simply supported footbridge subjected to a weak traffic scenario (0.2 pedestrians/m2), considering HSI and higher harmonics of pedestrians walking. The dynamic parameters of a single pedestrian, depicted as a Mass-Spring- Damper-Actuator (MSDA) system, and the modal parameters of the structure are employed to construct a coupled time-invariant crowd-structure system. The frequency-domain approach, based on a closed-loop Transfer Function (TF), considered in this study leads to a good agreement between numerical results and experimental outcomes obtained on an ultra-lightweight FRP footbridge. Thus, the proposed HSI model may be used as a first approximation to correctly estimate the dynamic response of other lightweight structures subjected to crowd-induced loads.