A Serviceability Analysis of Pedestrian Excitation on Light-Weight FRP Footbridges.

icubed’s Principal Structural Engineer Rohan McElroy is an expert in FRP design. He has been delivering and overseeing the design of FRP pedestrian, road, wharf and jetty infrastructure projects around Australia, New Zealand, UK, Canada, the USA, Fiji, Egypt and the UAE for the last decade. Based on his unique experience he has written this paper: “A Serviceability Analysis of Pedestrian Excitation on Light-Weight FRP Footbridges”.

As infrastructure becomes more advanced, lightweight materials such as Fibre Reinforced Polymer (FRP) are increasingly being used for pedestrian footbridges. However, the lightweight nature of these structures can cause concerns around pedestrian-induced excitation performance. In response to this, icubed consulting developed a method to assess accelerations in accordance with international research, using in-house software and procedures. We applied a pulsating force load to a 3D model of the bridge to replicate the vertical and horizontal impact of a footfall load, factored using formulas to evaluate the effect of multiple pedestrians walking in-sync and out-of-sync across the structure. The resulting graphs of maximum nodal accelerations were then compared to acceleration limitations outlined in other literature. We discovered that some in-sync load cases could amplify deck accelerations by a considerable amount. In-situ testing was also undertaken to compare theoretical models against actual performance.

FRP material has many benefits such as corrosion resistance, durability, termite resistance, light-weight, electrical and thermal insulation, high tensile strength, low embodied energy and a 100-year design life. Electrical-corrosion resistant (ECR) glass is used for reinforcing and vinyl ester resin for the matrix. FRP materials have different performance characteristics compared to other industry-standard construction materials, and the paper outlines the difference in performance between FRP and these materials.

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