18. Vibration Performance of Bridges Made of Fibre Reinforced Polymer

Due to favourable mechanical and physical properties, and the potential to provide a resilient and low-carbon infrastructure, fibre-reinforced polymer (FRP) material has increasingly been used for construction of highway and pedestrian bridges. Relative low mass, low damping and low stiffness make these bridges sensitive to dynamic excitation, which may lead to discomfort of human occupants and larger dynamic amplification of stress and deformation than is encountered in structures made of traditional structural materials. Consequently, design might be governed by a vibration serviceability state. Lack of data on vibration performance of FRP structures and non-existence of a state-of-the-art vibration serviceability design guideline means that current practice is conservative, often meaning only short-span FRP bridge solutions are executed. To fully exploit the benefits of using FRP material and to extend its use beyond current practice requires a better understanding of dynamic behaviour.

The objective of this paper is to study vibration performance of bridges made with FRP components. Two FRP footbridges having main spans of 15.6 and 63.0 m are used as case studies, and vibration behaviour is critically evaluated against steel/concrete structures of comparable span lengths. Both dynamic properties of the FRP and non-FRP bridges, as well as the vibration response under dynamic excitation by pedestrians, are reported. It is shown that the FRP footbridges could exhibit one order of magnitude larger vibration response under nominally the same dynamic loads. This finding highlights the need for timely research on the in-service vibration performance of FRP bridges with the aim of developing design guidance tailored for this newest structural material.