Investigation On Aero-elastic Effects Of Super High-rise Buildings By Wind Tunnel Test Of Bi-axial Forced Vibration

Nowadays, super high-rise buildings are rapidly developing towards the system with tall flexible structure, light mass and small damping ratio, and the non-liner aero-elastic effects induced by strong vibrations of the buildings under heavy wind actions have become the bottleneck for a precise evaluation of wind-induced responses and a fine wind-resistant design of the buildings.In this paper, models were drived by a bi-axial forced vibration device to simulate the vibration of high-rise buildings, pressure and displacement were measured simultaneously, and eight aero-elastic force coefficients were identified to study the effect of the amplitude, frequency and phase on the aero-elastic force, and the effects of vibration on the aero-elastic force in the direction orthogonal to the vibration.The main contents include:1? On the basis of Steckley one DOF forced vibration device, bi-axial coupled forced vibration device was developed, which can drive model do one DOF harmonic forced vibration and coupled forced vibration in two orthogonal directions. The pressure valve device can be built to scan the surface pressure of the vibration model, and displacement was measured by laser displacement meters, the problem of the pressure data and displacement data cannot be synchronized sampling was solved by "blowing method".2? Forced vibration wind tunnel tests of models with aspect ratio of 1:2,1:1 and 2:1, and three types of terrain category including uniform flow field, B, and D categories were completed, considering different combinations of along-wind and across-wind vibration frequencies and amplitudes, the effects of the one DOF vibration and bi-axial coupled vibration on the pressure coefficients, pressure spectrum, pressure coherence function and the drag and lift coefficient, power spectrum and coherence of lift and dragforce were analyzedin both amplitude and frequency domain. Based on the comparison between pressure correction amount of bi-axial forced vibration tests and MDOF aero-elastic model, the RMS pressure coefficient aero-elastic effect correction formula was proposed.3? Based on the forced vibration test of a single degree of freedom,the aero-elastic force coefficient, the modal aerodynamic damping ratio and modal aerodynamic stiffness ratio were identified by synchronization measured pressure and displacement, which are consistent with the literature, and results calculated by the time-domain integral method and complex aerodynamic impedance method showed a good consistency, which proves forced vibration test techniques, identification method and the corresponding recognition program in this paper reliability. Compared to the existing literature, this paper focused on the amplitude effects on the across-wind aerodynamic damping ratio, and across wind aerodynamic damping ratio formula considering amplitude correction has been proposed.4? For the bi-axial forced vibration with same frequency, the concept of nominal aerodynamic damping ratio was proposed, which is considering the effect of along wind vibration on the across wind aero-elasticforces, and therefore closer to the actual. For bi-axial vibration of different frequencies, aero-elastic coupling parameters were introduced to consider the impact of vibration in one direction on the self-excited forces in the direction orthogonal to vibration, and analytical methods of bi-axial coupled vibration system aero-elastic effects were established. Eight aero-elastic force coefficient rectangular cylinder were identified by bi-axial forced vibration tunnel test, in which coupling parameters are much small, for engineering applications only need to consider the across-wind aerodynamic damping coefficient, across-wind aerodynamic stiffness force coefficient and along-wind aerodynamic damping coefficient.5? Two-axial forced vibration wind tunnel test of a 347m-tall building were conducted.The along wind and across wind aero elastic damping and stiffness were identified, and aeroelastic effects on the wind-induced displacement response, acceleration response and equivalent wind load of the structure were calculated and analyzed. After considering the aeroelastic parameters acceleration response reduced by 10%.6? Meanwhile, multi-DOF aeroelastic model vibration test of the same building was conducted, and the along-wind and across-wind aerodynamic damping ratio were identified by using the random decrement technique,which were consistent with the results identified by the bi-axial forced vibration wind tunnel test. Combining with the load spectrum of the rigid model, the calculated responses considering aeroelastic parameters modification were closer to the experimental values of the aeroelastic model.