Effects of corner-recession on wind-induced responses and aerodynamic damping of a square megatall building under twisted wind flow

Modern super high-rise buildings have the characteristics of light weight and high flexibility, and their aeroelastic effects are very significant under strong winds. Nowadays, most super high-rise buildings adopt the aerodynamic treatments such as the corner modifications to reduce the wind loads and wind-induced responses. However, existing researches show that the wind direction will twist along the height, and it is not known whether the corner modifications still work when the building is immersed in the twisted wind flow (TWF). In view of this, the wind tunnel aeroelastic model tests were carried out on three multi-degree-of-freedom aeroelastic models with different cross-sections under the TWF with a wind twist angle of 25 degrees (25TWF). The effects of wind direction, reduced wind speed, and geometric shape modification on the aerodynamic damping ratio, extreme acceleration, and lock-in region are compared and discussed in detail. The results show that the wind direction has a great influence on the aerodynamic damping ratio, acceleration, and critical wind speed of vortex-induced resonance. It is found that the corner-recession treatment will suppress the occurrence of vortex shedding at 0 degrees wind direction, and significantly reduce the extreme corner acceleration. But the corner-recession is unfavorable in some wind directions (such as 30 degrees similar to 60 degrees) which may generate the vortex-induced resonance at a lower wind speed. This study contributes to a detailed insight into the effect of corner modifications on the vortex-induced vibration (VIV) phenomenon under twisted wind flow, furthermore, to provides useful information for further investigations and future wind-resistant designs of flexible structures.