Investigation on the effects of twisted wind flow on the wind loads on a square section megatall building

In most wind load codes, the wind direction is assumed to be the same along the height in the atmospheric boundary layer (ABL). But actually, due to the Earth's rotation (Coriolis force), the wind direction in the ABL changes along the height. This twisted wind flow (TWF) will obviously make a difference to the wind loads on megatall buildings. In this study, two kinds of TWFs with total wind twist angles of 25° and 15° are generated in a boundary layer wind tunnel. The effects of TWFs on wind pressures and aerodynamic forces acting on a square section megatall building model are investigated. It is found that the TWF significantly changes the distribution of wind pressure, and it makes the wind force that acts on the megatall building vary with the total wind twist angle. It is interesting to also find that the peak value of power spectra of the lateral wind force is also sharp in TWF. The wind direction where the sharp peak occurs merely changes from that in the corresponding equivalent straight wind flow (SWF). Also, the magnitude levels of correlation coefficient and coherence of wind forces in TWF are almost as strong as those in SWF. These factors further indicate that a relatively small wind-induced response may not be expected to be acquired in TWF. The results of this study have led to a comprehensive understanding of the effects of TWF on the characteristics of wind loads on a square section megatall building.