Aero-elastic Model Test For A Thousand-meter-scale Megatall Building And Analysis On Wind-induced Response

With the development of the urbanization, the construction of megatall buildings is growing vigorously. Generally speaking, the coupling relation between megatall building and wind load is so distinct that could generate aerodynamic negative damping. The damping would amplify the response which may threaten the safety of the structures. Accurate wind-induced response would be obtained by the aero-elastic model experiment which is the main method to analyze the fluid-structure interactions. At present, the study of the aero-elastic model experiments focuse on the buildings with rectangle cross section which are lower than 500 meter. While the research on the thousand-meter-scale megatall building with curved section, consisting of more towers is rare. The emphasis of the aero-elastic model experiment is to satisfy the similarity criterion of geometry, flow and dynamics between the model and prototype. While processing the model, it would be hard to meet all the requirements simultaneously, which would cause the errors in wind-induced response.The study focuses on the thousand-meter-scale megatall buildings, consisting of three equilateral-triangle arranged elliptic towers and a central circular tower. Designing the multiple degrees of freedom aero-elastic model and carrying on the wind tunnel test would be the first part. The second part is determining the correction factor of the aero-elastic model based on sensitivity analysis of similarity parameter to analyze the wind-induced response and the aero-elastic effect of prototype. The work consist several respects:1、The design of aero-elastic modelBased on similarity theory, geometry scale ratio of the aero-elastic model would be set to 1/600, frequency scale ratio would be 72.88, and the wind velocity scale ratio would be 1/8.23. Applying the method of equivalen t structure(containing skeleton columns, platforms and outer skin), the material property, section and position of skeleton columns and platforms are designed meanwhile. The modal parameters of aero-elastic model, containing frequency, model of vibration and damping ratio, are identified by the Hilbert-Huang transform method, the processing errors of aero-elastic models are analyzed meanwhile.2、The analysis of sensitivity of similarity parametersWithout considering the aero-elastic effect, establishing a ideal finite element model by ANSYS, time history analysis is adopted based on the data of wind tunnel pressure test. Taking the ideal finite model as the benchmark, the effect of single parameter respectively(mass and mass moment of inertia and frame column position, frame column section and damping ratio) to the sensitivity of wind-induced response is analyzed. Meanwhile, the correction factor between the aero-elastic model and ideal model are obtained.3、The analysis of wind-induced responses and aero-elastic effectAfter completing the wind tunnel experiments of aero-elastic modal of thousand-meter-scale megatall building, the wind tunnel results are corrected by the former correction factors. The relationship between displacement, acceleration and wind direction, wind velocity is analyzed, evaluating the safety and comfortableness of the structure. By the equivalent static wind load analysis of displacement and acceleration, the wind load factor(1.65) is obtained. Finally, considering the theory of vortex-induced vibration, the aerodynamic damping ratio, aerodynamic stiffness and other aero-elastic effect are analyzed and the critical reduced velocity of 7.96 is obtained.