Pedestrian induced vertical vibrations: Response to running using the Response Spectrum Method

Footbridges are increasingly prone to vibrations and designers are generally unable to predict pedestrian-induced vertical vibrations. Many aspects of human loading are infact not properly taken into account for in the load models employed by the international codes of practice, such as the randomness of crowds travelling across the footbridge. Moreover, the codes, for most of the part, do not deal with pedestrian loading other than walking, even though running and jumping can often produce larger loads and vibration amplitudes. In this paper, an investigation inot the response of footbridges under human-induced loading due to running is undertaken. To this end, Monte Carlo simulations are adopted for the generation of crowd loading. A reference response spectrum, defined as the peak acceleration associated with a given return period, is then developed. Correction factors are adopted to take into account variations in the structural characteristics, crowd morphology and return period. The correction factors, together with the reference acceleration, are used to determine the final response of the footbridge, for a given probability of load occurrence.