Nonlinear Parameter Identification On High-rise Building Wind-induced Based On Wavelet Theory

Nonlinear parameter identification method which based on wavelet theory in high-rise building model wind tunnel tests is introduced. By the comparative study of the two classic nonlinear systems——Duffing and Van der Pol, the free vibration form of the system is concluded both in damped and un-damped condition. Besides, the parameter identification method of the forced vibration which is under harmonic excitation is inferred as well. Taking Shanghai World Financial Center as its study object, using the figure of rigid model simultaneous manometry wind tunnel test and aeroelastic model vibration wind tunnel test as background, the system parameters of the model is identified and its stability is evaluated under the wind-induced effects.The main contents and work include:1、A brief introduction of two classic nonlinear systems——Duffing system and Van der pol system. It is demonstrated that Van der pol single-degree-of-freedom nonlinear systems is capable of similating the self-excited force of structure, damping, and amplitude under wind-induced effects. The Van der pol system is often used as the theoretical model of wind tunnel test. Several approximate analytical solutions to the nonlinear vibration equation are introduced, in which the mean value method is relatively convenient, and the analytical expression is accurate with small errors. Theoretical foundation based on complex Morlet wavelet transformation is introduced. Instantaneous vibration frequency and the expression of instantaneous amplitude can be obtained by extracting wavelets line using mold maximum method, which provides a mathematical model for identifying modal parameter of nonlinear systems.2n By identifying the un-damped and damping duffing system parameter, the validity of the chapter two can be verified from the numerical analysis aspect. Free vibration and forced vibration can be separate perfectly by extracting the wavelets line under harmonic excitation among the specific scale range. The mathematical model of Van der pol single degree freedom nonlinear systems is built and analyzed, and the identification error of system frequency is less than2%with relatively high accuracy. The nonlinear system would be transferred into linear system by harmonic linearization method. Then the linear coefficient will be imported to the nonlinear equations which also can identify the system parameters and obtain a favorable identified effect.3、Taking Shanghai World Financial Center as its study object, High-rise building rigidity model simultaneous manometry wind tunnel test and aeroelastic model vibration wind tunnel test are introduced. Based on continuous wavelet transformation method, the system wind induced displacement response is analyzed, and the damping factor, frequency and nonlinear small amount of the recognition system are identified. It can be included that the parameter identification of wind-induced nonlinear vibration as higher as precision based on continuous wavelet transform by comparing the result with initial excitation method, environment random vibration frequency domain method and time domain method, the identified results shows that the vibration of the model is unstable on the wind loads of135wind angle and9m/s wind speed, which explains the structure instability under the vortex-induced resonance case.