Experimental Study On Aerodynamic Coutermeatures Of Super High-rise Buildings Based On A New Type Of Aeroelastic Test Model

Super high-rise buildings have low fundamental frequency and low damping,and are prone to large vibration under the wind load,which significantly increases the design wind load and affects the living comfort.Measures must be taken to reduce the wind-induced response.Existing studies have shown that: aerodynamic measures are effective measures to reduce the wind-induced vibration response of high-rise buildings,and have the advantages of nice performance and easy operation.People often use aeroelastic model wind tunnel test to investigate the reduction effect of aerodynamic measures,but the single-degree-of-freedom aeroelastic model is mainly used to simulate the dynamic characteristics of super high-rise buildings（including damping ratio,mode shape,etc.）,which has poor accuraccy.For example,the model damping ratio is often above 2%,while the measured value on the buildings is often as low as 0.5%.In addition,the existing aeroelastic model tests mainly test the top acceleration response,which has limited reference value for actual engineering design.For this reason,this paper takes a 450 m high super high-rise building as the engineering background,and proposes a new super high-rise building aeroelastic model design method,which can realize the lowdamping and multi-modal simulation,and can simultaneously measure the top acceleration and base force of the model;on this basis,the vibration reduction effects of three aerodynamic measures such as corner recession,chamfered corner and rounded corner are studied.The main work content and conclusions are as follows:（1）Based on the similarity theory,a new design method for aeroelastic model of high-rise buildings is proposed.The cross-shaped core beam is used to simulate the stiffness.Under the premise of fully simulating the bending stiffness,the simulation of torsional stiffness is achieved as much as possible,and the internal connection nodes of the model are reduced.The ANSYS software platform was used to establish the dynamic characteristics of the aeroelastic model structure,and compared with the dynamic characteristics of the prototype structure to verify the rationality of the model design and optimize the model construction parameters.The aeroelastic model is processed and tested for dynamic characteristics.The test results show that the frequency of the model is in good agreement with the target value,and the damping ratio of the model is as low as about 0.4%.（2）The wind tunnel test of the aeroelastic model of a super high-rise building with a square section was carried out.Firstly,the relevant characteristics of the atmospheric boundary layer are introduced,and the C-type landform described in the Chinese "Building Structure Load Code" is simulated in the wind tunnel;the aeroelastic model wind tunnel test is carried out on the square-section building,and the base force response and the acceleration response under the wind attack angle from 0 to 45 is also obtained.The influence of the wind attack angle and wind speed on the wind-induced response of the square-section super high-rise building is studied,and the most unfavorable wind direction of the square-section super high-rise building is analysed.（3）Many aeroelastic model wind tunnel tests with three aerodynamic measures of corner recession,chamfered corner and rounded corner were carried out.Based on the designed aeroelastic model,12 corner optimization aerodynamic measures are selected,including three corner optimization methods: corner recession,chamfered corners,and rounded corners.Each corner recession type contains 4 different recession ratios;The effect evaluation index is defined to evaluate the control effect of the corner optimization measures,and compare the results with the code values and the results of related literature.The results show that the cross-wind equivalent static wind load results of the "Building Structure Load Code" are conservative;the corner optimization of the square-section building can reduce the average value of the downwind base bending moment and the root variance of the base torque by up to 30%.But it has little influence on the value of the root variance of the base bending moment.（4）Based on the aeroelastic model wind tunnel test,the optimal corner correction size is proposed.Taking the peak value of the base force response of the building as the target,the optimal corner recession ratio of the corner recession is 5%,which can reduce the base shear peak value by 15.7% and the base bending moment peak value by 13.7%;the optimal corner recession ratio of chamfered corner and rounded corner are both 7.5%,which can reduce the peak base shear force by 11.7% and 17.7%,respectively,and reduce the base bending moment peak by 10.9% and 17.0% respectively;in addition,for reducing the base torque peak,the chamfered corner with 10% recession ratio has the best effect.