Equivalent Dynamic Load Factor for Crowd Walking Loads

Abstract

Pedestrian-induced loads may cause vibration serviceability or safety issues in slender structures such as long-span floors and footbridges. Although some models for crowd walking loads have been established, the synchronization among pedestrians and interaction with the structure have not been fully expressed. This study proposes a Fourier series model with a series of equivalent dynamic load factors (EDLFs), which are adaptive to different crowd-dominant walking frequencies, structural damping ratios, crowd sizes, and pedestrian traffic conditions (unrestricted, restricted, and exceptionally restricted). Using the power spectral density for the crowd walking loads proposed in a previous study, the structural responses of different single-degree-of-freedom systems are calculated via numerical simulations of approximately 20 million variations, and the EDLF for crowd walking loads is obtained after back-calculating the structural responses. This modeling method weighted the energy around the dominant walking frequency. The results show that the EDLFs are stable for crowds of over 30 pedestrians. The proposed model was compared with three modeling methods for dynamic load factors and five codified models for crowd walking loads from different aspects, and the feasibility of the EDLF is verified based on a benchmark footbridge and an as-built floor structure. The EDLF is convenient for design purposes because it is compatible with the single-person model currently adopted in major design codes and software.