Crowd-structure interaction: Investigating the spatiality and synchronization of a pedestrian force model

Composite footbridges are slender civil structures that may be affected by the load action of walking pedestrians resulting in large deflections or even uncomfortable vibrations. There are several ways to model the load action of walking pedestrians on footbridges, but force-only models have been preferred by researchers and standards due to simplicity and good agreement with some measure data in real situations. However, there are some concerns relating to force only models as they do not capture important interaction effects between structure and pedestrians. Important features for force-only model implementation are often neglected by engineers such as the spatiality of the load application and the right synchronization among load components. These features bring more relevance for the simulated data and explain some structural behavior and discrepancies present in analysis using simple force-only models. In this paper, a fully synchronized force model for walking pedestrians is proposed and the effect of such model is compared with a simple force-only model and experimental vibration data obtained in a real composite footbridge. Pedestrians are treated as individuals with intrinsic kinetic and kinematic parameters that are correlated by a measured correlation matrix obtained by the use of a force platform for several pedestrians in laboratory conditions. Pedestrian parameters also follow defined Gaussian probability distribution functions with measured mean and standard deviation. A crowd situation is analyzed and the effect of the fully synchronized force model is assessed. The proposed force model provides a more accurate description of the walking forces applied by the pedestrians.