Co-authors​ :

 Senne STROBBE (BELGIUM), Wouter DE CORTE (BELGIUM), Peter VAN DEN BROECK (BELGIUM), Katrien VAN NIMMEN  

For the further development of prediction models for crowd-induced vibrations, it is imperative to obtain realis-tic and detailed information regarding representative loading conditions. Current guidelines only consider the force induced by crowds, neglecting the fact that the human body is a mechanical system that interacts with the supporting structure. Recent research shows that these human-structure interaction (HSI) effects, such as added mass and damping are significant when assessing vibration levels for footbridges. HSI phenomena have been assessed for crowd‐to‐structure mass ratios which are typical for steel footbridges. This work discusses a first step into the further development of models considering HSI effects for higher crowd-to-structure mass ratios, as encountered with fiber reinforced polymer (FRP) footbridges. Recent research shows that vibration serviceability is one of the most governing parameters in FRP footbridge design. Neglecting HSI-effects for these structures results in severe overestimations of the dynamic structural response, in turn leading to over-dimensioning of the bridge, unnecessary material usage and constraints on geometrical freedom.
The current work experimentally investigates the impact of HSI for an FRP footbridges. The experimental setup involved free decay tests to determine eigenfrequency and damping ratio of the coupled crowd-structure system. The tests were repeated for a relevant range of pedestrian densities, holding two body postures: (1) straight legs and (2) bent legs. Next to free decay tests, free walks and jogs were carried out, where the same groups of pedestrians traversed the footbridge for 5 to 10 minutes. The result of these tests are then compared to predicted response by design guides.