Estimating the Characteristic Vertical Response of a Flexible Footbridge Due to Crowd Loading

The issue of excessive vibration of footbridges due to pedestrian loading is now well documented. Bridge vibrations produced from a crowd of pedestrians have been estimated by modifying the effect caused by a single pedestrian by an enhancement factor to take crowd synchronization into account. In this paper this approach is extended to account for the fact that all pedestrians will not have the same pacing frequencies, and the effects of distributions of pacing frequency and other parameters on the enhancement factor are investigated. It is shown that this more faithful representation of pedestrian crowd walking behaviour gives reduced vibration response compared to the fully homogenous crowd case. Based on these results, enhancement factors for predicting the response due to a crowd from the predicted accelerations of a single pedestrian are proposed. Further, the results are compared with published test results to indicate that the model is reasonable.