# Effects of Corner Set--Backs on Wind Loads and Wind Induced Responses of Rectangular Tall Buildings
## 1 Introduction  
As the high-strength materials and innovative construction techniques are applied, high-rise building structures tend to be higher and more flexible. These high-rise buildings designed in strong wind regions will be sensitive to wind excitations. It has always been a problem in wind engineering to control or minimize the wind effect on high-rise buildings under strong winds [1, 2, 3]. There are three main approaches to reduce the wind load of high-rise buildings: auxiliary damping devices, structural measures and aerodynamic shape modifications [4]. Aerodynamic shape modifications refer to the adjustment of building geometry at the early stage of design to achieve the purpose of reducing wind effects from the sources [5, 6]. Corner set-back treatment is a popular corner modification for aerodynamic performance improvement during wind resistant design for high-rise buildings. [PERSON] [7] studied the aerodynamic instability of high-rise buildings with corner modifications through aeroelastic model tests, and indicated that a model with corner set-back rate of 5% is most effective in preventing the aeroelastic instability of high-rise buildings. [PERSON] and [PERSON] [8] examined the influence of corner modifications on square high-rise buildings through aeroelastic model tests and high-frequency equilibrium tests, and it was demonstrated that corner set-backs can result in a reduction in the peak of power spectral density in across-wind direction. The impact of different types of aerodynamic modifications on the wind effect of high-rise buildings was summarized by [PERSON] [9], who pointed out that the corner set-back modification can significantly reduce the wind-induced response alongand across wind directions. [PERSON] et al. [10] proved that the corner set-back modification could reduce base moment more effectively along and across wind directions. In this case, 14 square high-rise building models with corner set-backs were tested in two different simulated wind fields by [PERSON] et al. [11]. The test results show a significant effect of two types of corner set-backs on the aerodynamic coefficients of base moments and torques, and the best option for reducing the aerodynamic coefficients is a model having a corner set-back rate of 7.5%. Pressure tests have been conducted by [PERSON] et al. [12] in order to analyze the wind loads of corner set-back modifications on the high-rise buildings, the test results shown that a 10% corner set-back rate could best reduce the mean and RMS force in an along-wind direction. [PERSON] et al. [13] argued that the model with corner set-back generally has a better performance comparing the chamfered corners model in terms of lift force coefficient. [PERSON] and [PERSON] [14] revealed that building with corner set-back showed better performance to reduce drag force by numerical simulation. Although several research works have been conducted on corner set-backs on the reduction of wind loads and wind induced responses in tall buildings, further studies are still needed on this topic. On the one hand, the studies in the past mainly concentrated on the wind load characteristics of square high-rise buildings with corner set-back, and the associated findings are likely to be inappropriate for rectangular high-rise buildings duo to the difference in aspect ratios. On the other hand, the existing conclusions are lack of empirical formulas considering the effects of different corner set-backs, which can be applied to the assessment of wind effects reductions of high-rise buildings directly for engineering applications. Therefore, there is a need to systematically study the effects of different corner set-backs on the wind loads and wind-induced responses of rectangular tall buildings. In this paper, the benchmark model is the CAARC standard model, four other similar models with different corner set-back rates are designed accordingly.