Studies have shown that the presence of people modify the dynamic behavior of structures due to the addition of mass to the structure and also due to the ability of the human body to absorb energy, acting on the structure as a dynamic system of the type mass-spring-damper and justifying their representation through biodynamic models. The effect that people cause on the structure becomes more pronounced when the mass of persons is significant in comparison to the mass of the structure, as in the case of temporary grandstands. These types of structures have the lowest stiffness in the transverse direction. Thus, this study aims to examine the effect that the presence of people causes on the dynamic response of a temporary grandstand in the transverse direction, focusing on changes of the natural frequencies. A prototype of a temporary grandstand was assembled in the laboratory, with a capacity of about one hundred people. Modal tests were performed, and a finite element (FE) model of the structure was developed using the software ANSYS. Experimental data and results of the FE model of the grandstand with 5, 8 and 12 people seated were correlated to calibrate a biodynamic model representing each spectator. Such a model was a single degree of freedom (SDOF) system, departing from a biodynamic model proposed in literature, which was adapted to the condition of people in grandstands. Investigations were then performed on the vibrating properties of the structure when it was gradually filled with models representing the spectators. The results show significant changes on the transverse natural frequency when compared to that of the empty structure, demonstrating the importance of considering the effect of people in temporary grandstands and its representation through biodynamic models.
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