Human-induced loading and dynamic response of footbridges in the vertical direction due to restricted pedestrian traffic

Despite extensive research in the field of human-induced vibration in the last twenty years, there is still lack of reliable load and response models to assess vibration serviceability of footbridges under human-induced excitation, especially with reference to crowded conditions. This paper aims to provide a reliable characterization of pedestrian-induced loading on footbridges in restricted traffic condition, and to compare the reliability of current guidelines and advanced spectral models in the serviceability assessment of footbridges with respect to vertical vibrations. Numerical simulations of restricted pedestrian traffic are carried out through an agent-based model, considering variable pedestrian densities and deck widths. The probability distribution of the step frequency and the power spectral density function of the modal force are obtained numerically. Based on the numerical results, a Modified Generalized Equivalent Spectral Model is proposed. Finally, two numerical examples are analyzed to assess the reliability of current guidelines and of the Modified Generalized Equivalent Spectral Model in the estimate of the maximum footbridge acceleration.