Slender buildings gallop in the wind
Slender buildings gallop in the wind lead image
To maximize land efficiency in cities, high-rises are built on shrinking footprints. The aspect ratio quantifies the building’s height compared to its footprint: the higher the aspect ratio, the slenderer the building. However, the across-wind instabilities, known as aeroelastic behaviors, of slender skyscrapers with aspect ratios over 10 have not been thoroughly studied.
Shan et al. investigated the effect of urban flow across winds on tall-square towers with aspect ratios of 12, 16, and 20. They tested miniature models of these towers in a wind tunnel simulating urban flow with high turbulence intensity, which describes the intensity of wind velocity fluctuation. With an aspect ratio of 12, the shortest tall-square tower did not exhibit aeroelastic behaviors. This is likely because the high turbulence intensity in urban flow mitigates them.
However, the authors found that as building height and aspect ratio increase, so do aeroelastic behaviors due to across wind. The tall-square towers with aspect ratios of 16 and 20 exhibited strong oscillations known as across-wind galloping. This suggests that once the aspect ratio of a tall-square building is beyond a threshold located somewhere between 12 and 16, the large turbulence intensity in urban flow does not mitigate aeroelastic behaviors.
This work could act as a reference for those attempting to design slender tall-square buildings in cities.
“This paper has carefully discussed the across-wind instabilities of tall-square towers, which is necessary for the wind-resistant design of tower-like structures, such as skyscrapers and so on,” said author Kunpeng Guo.
Next, to further clarify the underlying mechanics and better predict wind responses of slender buildings, pressure measurements for static and aeroelastic tests must also be considered.
Source: “Across-wind response characteristics of tall-square towers in urban flow: An experimental study focused on the aeroelastic effects,” by Wenshan Shan, Qingshan Yang, Kunpeng Guo, Cong Chen, Wei Zhen, and Yong Chul Kim, Physics of Fluids (2024). The article can be accessed at https://doi.org/10.1063/5.0194289 .
This paper is part of the open Flow and Civil Structures Collection, learn more here .
