Simple equation to account for the human-structure interaction effects on the modal damping of footbridges

Resumo

Footbridges dynamic properties may be affected by the presence of pedestrians, especially the modal
damping of the occupied structure which is greater than that of the isolated one. To account for this increase,
particularly in lightweight and slender footbridges, which are susceptible to the human-structure dynamic
interaction (HSI), the pedestrians are modelled as a mechanical system coupled to the footbridge model. In this
paper, an equation is proposed to add the damping contribution provided by persons walking on footbridges to the
isolated structure damping ratio. The presented equation is based on numerical results obtained from a
computational tool especially developed to address the effects of HSI. A comparison of the damping ratio obtained
with the proposed equation and the experimental measurements in a slender footbridge from the literature is
favorable. The estimated damping ratio of the coupled system (footbridge plus pedestrians) could then be used to
include the HSI effects to existing design methodologies based on the live load approach to simulate pedestrian
forces.