Abstract Summary
Despite extensive research in the last twenty years, there is still lack of reliable models for human-induced excitation, especially with reference to crowded conditions. Guidelines provide equivalent resonant uniformly-distributed loading with an increased loading amplitude for high density in order to account for the possible synchronization among pedestrians in very dense traffic conditions. This very simple loading condition does not take into account the variation of the walking velocity and step frequency with pedestrian density and may lead to unreliable predictions of the vibration level. A reliable human-induced loading model on footbridges taking into account pedestrian interaction requires experimental tests on full scale structures, that are scarce in the literature and limited to low pedestrian densities [1]. In the literature, experimental tests in straight corridors have been carried out, both in the case of unidirectional (e.g. [2]) and bidirectional traffic (e.g. [3]), providing fundamental diagrams of the mean walking speed as a function of pedestrian density. As an alternative to experimental characterization , numerical simulations based on suitable crowd dynamics models can be carried out (see, e.g. [4], limited to unidirectional pedestrian flow). The authors of the present paper carried out a wide campaign of numerical simulations of unidirectional and bidirectional pedestrian traffic through an agent-based model, considering variable pedestrian densities and deck widths [5]. The present paper has two distinct objectives: 1) to validate the results of numerical simulations carried out by the authors against the experimental measurements available in the literature, 2) to adopt the results of numerical simulations of pedestrian traffic in order to assess the reliability of guidelines’ predictions. Two structure case studies are considered, pedestrian-induced forces are derived from numerical simulations of pedestrian traffic and the footbridges’ dynamic response is calculated for different levels of pedestrian density. Then, the dynamic response obtained from numerical simulations is compared with guidelines’ predictions in order to assess their reliability in vibration serviceability assessment of footbridges. REFERENCES [1] K. Van Nimmen, J. Hauwermeiren and P. Van den Broeck, “Eeklo Footbridge: benchmark dataset on pedestrian-induced vibrations”, Journal of Bridge Engineering ASCE: 05021007 (2021). [2] J. Zhang, W. Klingsch, A. Schadschneider and A. Seyfried, “Transitions in pedestrian fundamental diagrams of straight corridors and T-junctions”, Journal of Statistical Mechanics: Theory and Experiment: P06004 (2011). [3] T. Kretz, A. Grunebohm, M. Kaufman, F. Mazur, M. Shreckenberg, “Experimental study of pedestrian counterflow in a corridor”, Journal of Statistical Mechanics Theory and Experiment: P10001 (2006). [4] E. Bassoli, L. Vincenzi, “Parameter calibration of a Social Force Model for the crowd-induced vibrations of footbridges”, Frontiers in Built Environment, doi: 10.3389/fbuil.2021.656799 (2021). [5] F. Venuti and F. Tubino, “Human-induced loading of footbridges due to restricted pedestrian traffic: probabilistic characterization and equivalent spectral model”, Structure and Infrastructure Engineering, doi: 10.1080/15732479.2021.1897630 (2021).
