Experimental and numerical serviceability assessment of a steel suspension footbridge

The paper summarizes the main results of the serviceability assessment of a steel suspension footbridge, performed through dynamic testing and numerical simulations. The experimental part of the study involved both operational modal testing and measurement of the structural response under the crossing of different groups of pedestrians. The footbridge exhibited quite complex dynamic characteristics (i.e. two couples of closely spaced modes and five modes in the frequency range 1.9–3.0 Hz) and the maximum accelerations induced by pedestrians and joggers turned out to be in the range of discomfort. An accurate FE model, based on the design drawings, was then developed and a general procedure is proposed to tackle the crucial issue of assigning the design tension forces to the suspension elements. Since the comparison between numerical and experimental results generally shows a good agreement, the model is adopted to perform a numerical assessment of vibration serviceability according to the European guideline HiVoSS. A minor shortcoming of HiVoSS and the unusual relevance of the 2nd harmonic of pedestrian-induced load are highlighted for the investigated footbridge.