Footbridge vibrations and their sensitivity to pedestrian load modelling

Pedestrians may cause vibrations in footbridges, and these vibrations may potentially be problematic from a footbridge serviceability point-of-view. Foreseeing (already at the design stage) unfit conditions is useful, and the present paper employs a probability-based methodology for predicting vibrational performance of a bridge. The methodology and the walking load model employed for calculation of bridge response accounts for the stochastic nature of the walking parameters of pedestrians (step frequency, step length etc.) and the end result is central statistical parameters of bridge response (quantiles of bridge acceleration) to the action of a pedestrian. The paper explores the impact that selected decisions made by the engineer in charge of computations have on the statistical parameters of the dynamic response of the bridge. The investigations involve Monte Carlo simulation runs as walking parameters are modelled as random variables and not as deterministic properties. Single-person pedestrian traffic is the load scenario considered for the investigations of the paper and numerical simulations of bridge accelerations are made for artificial but realistic footbridges.