Abstract Summary
Human-induced vibrations in slender lightweight footbridges have been extensively investigated in the last 30 years. In existing guidelines, such as SETRA or HIVOSS, the dynamic response of a footbridge can be assessed considering the pedestrians as external non-interacting loads acting on the structure. For a more realistic load model, individuals defined as single Degree of Freedom (DOF) dynamic systems have been employed by several researchers and practitioners. Hence, Human-Structure Interaction (HSI) is accounted for the response prediction of a footbridge. Adopting this modelling approach to calculate the footbridge vibration levels may lead to a costly computational problem when dealing with a crowd due to the large number of DOFs associated to the pedestrians. Recently, a frequency-domain procedure based on a crowd-structure system has been proposed by the authors to overcome the aforementioned issue. To further validate the proposal, the computed results should be contrasted with experimental measurements. In this sense, this paper presents the dynamic response of two footbridges under the action of streams of walking pedestrians. A laboratory structure formed by Fibre Reinforced Polymer elements is firstly analysed, and an in-service cable-stayed steel footbridge is secondly studied. The vibration serviceability limit state of both pedestrian structures is assessed considering 0.20 pedestrians/m2 (weak traffic) and 0.50 pedestrians/m2 (dense traffic). For each footbridge, the performed experiments are described, and the corresponding recorded measurements are presented. Then, the experimental results are compared with predictions computed through the application of load models from existing guidelines. In addition, the frequency-domain proposal is employed to calculate the structural response while accounting for HSI. Since parameters of the human body must be defined for the last approach, different values available in literature are employed. Outcomes demonstrate the overestimation of the response when provisions stated in current design documents are used, and the benefits of the novel procedure to consider Crowd-Structure Interaction on lightweight footbridges are highlighted.
