Measured dynamic properties of web-core sandwich panel FRP composite footbridges and their relation to pedestrian comfort analysis

摘要

This paper reports experimental data for the dynamic properties (i.e. first fundamental flexural frequency, damping ratio, comfort class) of ten web-core sandwich panel FRP composite footbridges in Belgium, which contributes to the assessment of relevant input parameters for design and assessment of this promising bridge type, quickly gaining popularly in recent years. The data is gathered based on smartphone accelerometers, enabling easy, quick, affordable, and abundant measurements, while at the same time yielding reliable experimental values. Given the relatively short spans, the heel and excitation test methods are used, rather than the ambient vibration method. The tests indicate damping ratios of one to three percent, which are strongly dependent on the number of people on the bridge during the measurement. Additionally, comfort analysis tests with up to 58 people (0.5P/m(2)) were conducted on five out of the ten bridges. The results indicate that the current design guidelines for pedestrian comfort analysis are overconservative and do not reflect the effect of pedestrian-induced damping, which is especially apparent for this bridge type given its very low modal mass and relatively low damping ratio.