Biodynamic single person and crowd pedestrian model: a worked test case and simulation

The structural design of footbridges usually employs mathematical models to represent the structure and applied loads. Regarding the pedestrian loads, standards and guidelines currently recommend applying forces onto the structure, including those due to a stream of pedestrians.

However, for the vibration serviceability limit state, recent studies have shown evidence that the mass and the capacity to dissipate mechanical energy of the human body may play a significant role. To account for these additional contributions, biodynamic models consisting of mass, stiffness and damping can be used to represent the full action of pedestrians, beyond the forces they apply.

In order to verify the influence on the response, due to the action of pedestrians represented by biodynamic models, measured accelerations due to a single person crossing a stressed ribbon footbridge were compared with respective accelerations obtained through a finite element model of the structure. This was made by representing the pedestrian action only by forces and also by forces and a biodynamic model. In addition, simulations were carried out for a stream of pedestrians, using a crowd density of 0.3 pedestrians/m².

It was observed that the action of pedestrians changed when biodynamic models were introduced. This occurred for the load case of a stream of pedestrians, resulting in reductions of accelerations around 50% for the first vibration mode.