To account for vertical human-structure interaction (HSI) in the vibration serviceability analysis, the
contact force between the pedestrian and the structure can be modelled as the superposition of the force
induced by the pedestrian on a rigid surface and the force resulting from the mechanical interaction
between the structure ...
To account for vertical human-structure interaction (HSI) in the vibration serviceability analysis, the
contact force between the pedestrian and the structure can be modelled as the superposition of the force
induced by the pedestrian on a rigid surface and the force resulting from the mechanical interaction
between the structure and the human body. For the case of large crowds, this approach leads to (timevariant) models with a very high number of degrees of freedom (DOFs). To simplify analysis, this paper
investigates the performance of an equivalent single-degree-of-freedom approach whereby the effect of
HSI is translated into an effective natural frequency and modal damping ratio for each mode of the
supporting structure. First, the numerical study considers a footbridge structure that is modelled as
a simply-supported beam for which only the fundamental vertical bending mode is taken into account.
For a relevant range of structure and crowd parameters, the comparison is made between the structural
response predicted by the simplified model and the more accurate reference model that accounts for all
DOFs of the coupled crowd-structure model. Where the simplified model is found to underestimate the
structural response, although to a limited extent, this is compensated for by introducing a correction
factor for the effective damping ratio. Second, the performance of the simplified method is evaluated
through the application on a real footbridge. The results show that the simplified method allows for a
good and mildly conservative estimate of the structural acceleration response that is within 10-20% of
the predictions of the reference crowd-structure model.
