Effect of three-dimensionality of turbulence on the along-wind loads of square cross-sectional structures

The existing theories for along-wind loads on slender structures, based on the “strip assumption” overlook the three-dimensionality of turbulence. However, numerous experimental phenomena contradicting the “strip assumption” highlight the need to consider the effects of three-dimensional turbulence (3D effect). This study develops an analysis model that considers the three-dimensionality of turbulence and derives a function containing the section-shape-dependent characteristic parameters to represent the 3D effect. A method for identifying the parameters through a wind tunnel test is proposed to solve this function. The parameters for the square cross section are then identified in two different turbulence fields, revealing that the identification parameters of both cases are nearly identical. This similarity indicates that the parameters are independent of the turbulence validating the proposed theories. Finally, the 3D effect on square cross-sectional structures with different aspect ratios under various turbulence integral scales is analyzed. The results showed that as the ratio of the turbulence integral scale to the windward width of the structures increases, the 3D effect reduces, but the rate of reduction slows down. In addition, increasing the aspect ratios of structures further mitigates the 3D effect, enhancing the accuracy of the “strip assumption.” These results can be a reference for evaluating the accuracy of the “strip assumption” theory for square cross-sectional high-rise buildings in atmospheric boundary layer turbulence. The proposed method can be applied to investigate the 3D effect on along-wind loads of slender structures with various cross-sectional shapes.