Modal Analysis of Flax Fiber Reinforced Composite Bridge Using FEA to Support the Design of the Target Bridge Made of Innovative Material

This paper presents a comprehensive modal analysis of a 15-meter span footbridge constructed using fiber-reinforced polymer structures (FRPs) integrated with natural resource fibers and a partial bio-based resin. The bridge was erected at the Floriade Expo 2022 located in Almere, the Netherlands. The lightweight nature of FRPs, coupled with their sensitivity to vibrations, necessitates the satisfaction of specific design requirements to ensure the safety and comfort of pedestrians. The initial phase of this study entails determining the natural frequencies of the bridge via Finite Element Analysis (FEA). Comparative assessment between the footbridge's natural frequency and excitation frequencies evaluates the risk of resonance induced by pedestrian loading. The FEA employs a composite layup technique to replicate the same ply configuration as the actual bridge model. Following the initial assessment, a comprehensive analysis is undertaken to meticulously examine the dynamic response of the footbridge. This analysis prioritizes the evaluation of critical acceleration parameters under diverse conditions, encompassing scenarios such as walking, jogging, and crowded pedestrian traffic. Bridge peak acceleration is assessed and juxtaposed against design values based on site usage, route redundancy, and structural height, and for the target bridge is 0.77 m/s². The results indicate that the footbridge successfully fulfills the specified design criteria for ensuring pedestrian comfort under various dynamic loading conditions. This finding underscores the significance of including the footbridge in the building application process. This study underscores the successful application of FRPs, augmented with natural fibers and bio-based resin, in ensuring the structural integrity and comfort of footbridges subjected to real-world dynamic conditions.