Modeling and experimental study on walking human-structure interaction systems subjected to earthquake excitations

The adverse effects of crowd activity on the structural response observed in several accidents have raised our concern about the role of human-structure interaction (HSI) on the seismic response of structures with dense crowds. To this end, a series of experimental campaigns and numerical studies have been conducted to investigate this phenomenon. In shaking table tests, participants walked individually on either a stationary or longitudinally vibrating treadmill, and their responses were measured. In particular, to better represent the HSI, a shaking table real-time hybrid testing (RTHT) was proposed and applied to evaluate the seismic response of the HSI system. A bipedal spring-loaded inverted pendulum (BSLIP) is then applied to simulate human behaviors. The experimental results indicated that the HSI in the longitudinal direction can be interpreted as additional positive mass and positive damping to the structure. Moreover, the RTHT showed that the human step frequency underwent significant changes when subjected to ground vibration, and synchronization occurred when the human step frequency was close to the structural vibration frequency, leading to a notable impact on the structural response. The numerical results show BSLIP model can represent both non-synchronization and synchronization responses of the human body, as well as effectively capturing the coupling between the longitudinal and vertical directions. Finally, the comparison between simulation and RTHT further confirms that the proposed BSLIP model is reliable to evaluate the seismic response of the HSI system.