Load capacity and serviceability conditions for footbridges made of fibre-reinforced polymer laminates

Abstract

The contribution is focused on derivation of the Ultimate Limit State (ULS) and Serviceability Limit State (SLS) design criteria for footbridges built of fibre-reinforced polymer matrix (FRP) laminates. The ULS design criterion is based on the design guidelines for above-ground, pressure, FRP composite tanks and the Tsai-Wu failure criterion, which is used to predict the onset of FRP laminates damage. The SLS criterion is based on vertical deflections and natural frequencies limitations of the analysed FRP footbridge. As a part of the research, a special design procedure is established for FRP footbridges design process, covering both the preliminary and detailed engineering calculations. As an illustrative example, the procedure is applied to glass-fibre reinforced vinylester laminate with 90°C heat deflection temperature and 50-year service life. A deflection-based serviceability limit state criterion is established using the same approach as that currently used in the design of steel footbridges. Moreover, the second serviceability limit state criterion is proposed. It limits the range of possible fundamental natural frequency of footbridge without any load and loaded with an additional mass 70 kg/m2 applied to simulate load created by moderate pedestrian traffic.