Experimental Study On Aeroelastic Model Of Thousand-Meter-Scale Megatall Buildings Under Twisted Wind Flow

Industrialization in the 21st century has promoted the concentration of population in cities,the demand for social development,and the application of new materials and new technologies have enabled urban architecture to break the limits of construction.More and more super high-rise buildings continue to emerge,the record of the world’s tallest building constantly being refreshed.Looking at the development at home and abroad,the development of super high-rise buildings to a height of kilometers or even higher has become the trend of international architecture in the future.When the height of the building reaches the kilometer level,due to its characteristic of high slender ratio and high flexibility,resonance is easy to be intrigued by the vortex-induced vibration(VIV),and wind load will become a key factor in structural design.Existing studies have shown that the horizontal wind direction will twist significantly with height.Then,the fluid-structure interactions(FSI)and the twisted wind effect will work together.Therefore,the results based on the straight wind flow(SWF)cannot accurately reflect the wind of the super high-rise building under the real wind field.Load and wind-induced response characteristics.Therefore,it is necessary to conduct research on the aeroelastic effect of thousand-meter-scale megatall buildings under the twisted wind flow,so as to fill the gaps in related research.The aeroelastic model wind tunnel test method is the main method to study the aeroelastic effect of thousand-meter-scale megatall buildings,which can obtain accurate structural wind-induced response and aerodynamic damping ratio.This paper uses a self-designed aeroelastic model and wind tunnel test to explore the mechanism of aeroelastic effect under twisted wind flow,the main research content has the following three aspects:1.Using the“Mega frame-Core tube-Outrigger truss”structure system,a three-dimensional finite element model of a thousand-meter-scale megatall building is established based on ANSYS software;the equivalent structure method of“Skeleton column and Rigid platform and Coat board”is used for a 5-column multi-degree-of-freedom aeroelastic model.The frequency of model can be adjusted freely,moreover,under the condition of the same dynamic characteristics,the cross-sectional shape(square,corner-recessed square,double-corner-recessed square)can be transformed freely,which greatly saves the test cost and time;the hammer test was carried out,the modal parameters of the aeroelastic model were identified by the Hilbert transform method and the peak picking method,and a ideal aeroelastic model was obtained;the twisted wind flow with a twisted angle of 25~oand the corresponding straight wind flow were simulated in the wind tunnel,and aeroelastic model wind tunnel test was conducted.2.Using genetic algorithm to improve the selection method of amplitude and sample length in random decrement technology(RDT),combined with Hilbert-Huang transform method to identify aerodynamic damping ratio;The frequency domain analysis of the atop acceleration of the thousand-meter-scale megatall building aeroelastic model under the twisted wind flow at different incoming wind speeds is carried out,and the vortex-induced resonance area is determined.Finally,the influence of the wind direction angle,cross-sectional shape,and structural frequency on the model X-axis,Y-axis and torsion direction is analyzed.This study found that the combined extreme acceleration of the square aeroelastic model at a wind twisted angle of 75~o under 25TWF is about twice the wind direction angle of 15~o,and there are obvious peaks at 30~o,45~o,and 60~o,which are 0.127 m/s~2,0.133 m/s~2 and 0.125 m/s~2,respectively.The corner-recessed and double-corner-recessed suppressed the occurrence of vortex shedding at a wind direction angle of 90~o in the X direction,and the RMS of acceleration were reduced by 64.4%and 62.9%,respectively.3.The influence of wind direction angle and building shape on wind-induced response and aeroelastic effect of thousand-meter-scale megatall buildings under twisted wind flow and straight wind flow are compared.In addition,the relationship between the vortex-induced vibration“lock-in zone”and critical wind speed changes under the two wind flows is compared,which provides a useful reference for the wind resistance design of thousand-meter-scale megatall buildings.