Vertical Vibration Response of Footbridges with Fundamental Natural Frequency up to 10 Hz under Dynamic Loading by Single Pedestrian

A design spectrum of characteristic acceleration response to pedestrian-induced dynamic loading has been developed for footbridge structures. The novelty of the proposed spectrum over the existing spectra is that: (1) it is underpinned by a recently developed comprehensive statistical model of pedestrian dynamic loading; (2) it is applicable to a broader natural frequency range of structures up to 10 Hz; and (3) it accounts for uncertainties in both dynamic loading and structure dynamics that are typically encountered in structural design. In addition, the importance of correct modeling of pedestrian's walking speed and narrow-band nature of the force signal has been demonstrated. Comparison with the design spectra recommended in contemporary design codes reveals that the existing approaches are not being applicable for structures with natural frequency in the range of third, fourth, and fifth harmonic of the dynamic force. In addition, they could both underestimate and overestimate the structural response for lower-frequency structures. The proposed design spectrum is a design tool applicable to structures whose mode shape can be approximated by half-sine, span length between 12.5 and 100 m, and damping ratio between 0.25% and 2%.