Experiment And Theory Of Human-structure In Horizontal Vibration

With the wide application of advanced materials and technologies in the field of civil engineering, the architectures tend to be with larger span and bigger space. Such advanced materials used to build the modern archetectures are usually with high strength/weight ratio. However, this leads to the lower natural frequency of these structures, which can cause excessive vibration under the loads of people. For example, footbridge, sports venue and temporary grandstand are often excited to vibrate, which not only affects the comfort since people can feel the vibration, but also run the risk to cause collapse of those civil structuers causing big loss in lives and properties. This has motivated many researchers to work on the research of human-structure interaction mechanism. In this paper, the horizontal vibration characteristics of human-structure system were studied by the test of horizontal vibration. with changed natural frequencies since people have two status, standing and sitting, during the test.. The theory model of the coupling vibration of the human-structure system was established and the theoretical model was validated by the experimental results. The main research content of this paper and the main conclusions are summarized as follows:(1) The horizontal vibration characteristics of human-structure system were studied experimentally in the case that people were standing naturally. Besides, the coupling vibration model of human-structure system was discussed as well. Test content includes: the vibration characteristics of mass-structure system; the vibration characteristics of single-people-structure system, double-people-structure system, three-people-structure system and four-people-structure system under the condition varied structural natural frequencies by changing the stiffness of tested structures. The results showed that: the additional mass block can cause the significant reduction of structural frequencies, while the damping ratio was changed only a little; when one people standed staticly on the tested structure, the reduction in the fundamental frequency was different depending on the facing direction of the person while the damping ratio was remarkably increased in the human-structure system; the fundamental frequency of all the single-, double-, three-, four-people-structure systems showed a downward trend while the damping ratio tends to increase.(2) Coupling vibration model of human-structure system in the horizontal was researched. Present research has also established the mass model, the mass-spring-damper model, and the mass-spring-damper-additional rigid mass model to simulate the dynamic model of human body, and then a coupling model of human and structure was constituted. The mass-spring-damper-additional rigid mass model was proved to be more accurate by comparing the results of theoretical analysis with the test results. In addition, the average frequencies of the human body in either horizontal back-forth or left-right directions were calculated according to the test results.(3) The horizontal vibration characteristics of human-structure system were studied experimentally in the case that people were sitting naturally. The vibration characteristics of single people-structure system was tested and analyzed under the condition that the structure has varied natural frequencies by changing the structural stiffness. The results show that a mode or two modes appeared due to different structural fundamental frequency and different facing direction of the tested candidates when people sitted staticly on the structure. Compared to single person standing naturally, the condition of sitting provides more damping to the structure. Finally, by referencing the comparison between the test and the theoretical results of a standing body-structure system, it was concluded for the sitting body-structure system that a sitting body can be treated as a mass-spring-dampe-additional rigid mass under the lateral vibration conditions.