Effects of the body force on the pedestrian and the evacuation dynamics

Abstract

The Social Force Model (SFM) is a suitable model for describing crowd behaviors under emotional stress. This research analyzes the role of the body force in the original SFM. We focused on the parameter associated with the body stiffness (kn) and its impact on the pedestrian dynamics for two different geometries: bottlenecks and corridors. Increasing kn produces opposite effects on the crowd dynamics for each geometry: an increase of the crowd velocity for bottlenecks, and a decrease for corridors. The former reflects the fact that an increase in the stiffness reduces the overlap between pedestrians and, as a consequence, the sliding friction is diminished. This phenomenon reduces the number of blocking clusters close to the exit door. In the case of the corridor, instead, due to the confining walls, the pedestrians get tight into a lattice-like configuration due to space limitations. The friction interaction with the walls determines the velocity of the whole crowd along the corridor. Additionally, the corridor geometry generates a flux slowing down for very crowded environments, as observed in many real-life situations. We also explored the contact forces parameter values (body force and friction coefficients) and tuned them to reproduce the qualitative behavior of the empirical fundamental diagram.