Dynamic loading and response of footbridges

Abstract

Dynamic forces were measured during walking, running, and jumping, using an instrumented platform. The results are expressed as sinusoidal force amplitudes normalized by the subject's weight and are plotted versus frequency. The maximum dynamic loads for walking were found to be nearly twice as large as those recommended in the 1983 Ontario Highway Bridge Design Code or the British Standard BS5400, and those for running or jumping, more than six times as large.Responses of footbridges are calculated using a simple formula based on the dynamic loading due to one person, the response of a simple span at resonance, and limited duration of excitation. Good agreement was obtained with the measured response of two 17 m experimental spans subjected to human excitation, for both the first and second harmonics of the step rate. The resonant vibrations of the spans can be substantially reduced by resonant dampers. Key words: footbridges, dynamic loads, dynamic response, design criteria, resonant dampers.