Avaliação do comportamento estrutural dinâmico não determinístico de edifícios altos submetidos à ação do vento

Abstract

In recent decades, major Brazilian cities have experienced significant growth in the development and construction of tall and slender buildings. This architectural trend, driven by the need to optimise urban space and the pursuit of aesthetic innovation, has resulted in more flexible structural systems with considerably low natural frequencies, making them more susceptible to issues related to excessive vibrations caused by the dynamic action of wind. Accordingly, this research aimed to evaluate the dynamic structural behaviour of tall buildings under nondeterministic wind loads, taking into account soil-structure interaction, geometric nonlinearity, and aerodynamic damping due to the relative motion between the structure and the wind. This was achieved through the development of a methodology that simultaneously considers these effects in the dynamic analysis. A statistical treatment was applied using an appropriate number of wind load series, given the nondeterministic nature of these loads. To obtain the dynamic structural response of tall buildings, a case study was conducted involving a composite steel and concrete building with 48 storeys and a height of 172.8 metres. A numerical model of the building was developed using the finite element method and the ANSYS software, incorporating fixed supports and foundation modelling to achieve a more realistic representation of the structural system and to account for soil-structure interaction effects. A parametric analysis of the dynamic structural response was carried out, considering a wind velocity range from 5 to 45 m/s, covering a substantial portion of the basic wind velocities indicated in the NBR 6123 (1988) isopleth. The evaluation of the dynamic structural response, including maximum displacements and human comfort, was based on natural frequencies, average maximum accelerations, and displacements. The study concluded that the effect of soil-structure interaction on the analysed building model was not significant in terms of dynamic structural response. Furthermore, geometric nonlinearity resulted in notable differences in the building’s dynamic response, with maximum variations ranging from 5 to 30% for displacements and from 15 to 45% for accelerations, considering basic wind velocities from 5 to 45 m/s in 5 m/s intervals. This effect should therefore be considered in the design of tall buildings. On the other hand, the contribution of aerodynamic damping was not significant, with maximum differences of up to 5% for horizontal translational displacements and up to 10% for accelerations. A human comfort assessment was conducted based on the criteria of Hirsch and Bachmann (1995) and the standards ISO 2631 (1997), NBR 6123 (1988), and NBR 6123 (2023), indicating that there are differences in the human comfort range among the adopted criteria. In particular, when comparing the 1988 and 2023 versions of NBR 6123, significant differences in acceleration magnitudes were observed, with reductions in the order of 37 to 52%, considering basic wind velocity intervals from 5 to 45 m/s.