Non-Stationary Seismic Response Analysis Of Wind Power Tower Based On Wavelet Evolutionary Power Spectrum

With the development of wind energy,modern wind power towers tend to have higher single-unit capacity and higher height from the ground,and many wind power towers are built in seismically active areas.A large number of seismic records show that earthquakes are random and non-stationary.In order to evaluate the seismic response of wind tuebine structure rationally,it is necessary to study its non-stationary seismic response time-frequency characteristics.Based on the wavelet theory,the non-stationary random dynamic response of 2MW onshore wind power tower is analyzed in this study.Firstly,the theory of estimating Evolutionary Power Spectral Density(EPSD)of structural dynamic response by wavelet transform is presented,and the random dynamic response of the top of a 1/20 scale model wind turbine tower under random earthquake action is analyzed.According to the physical and geometric parameters of the scaled model,the finite element model of the wind turbine tower is established.The response of the tower top is solved by programming codes based on the Newmark-β integral method.The results are compared with the test results,the accuracy and reliability of the finite element model are verified.Secondly,based on wavelet theory,the joint time-frequency distribution of elastic dynamic response energy of the tower top under random excitation with different impulse contents is analyzed.The results show that with the increase of the number of pulses,the amplitude of EPSD increases and the distribution of evolution spectrum is significantly different.The attenuation of the response at the top of the tower is relatively slow with the pulse.Thirdly,the elastic-plastic finite element model of the wind tower is established based on the elastic-plastic constitutive relation of steel.The elastic-plastic dynamic responses of structures under different Peak Ground Acceleration(PGA)are calculated and the EPSD is estimated.The results show that the elastoplastic behavior of the structure can improve its energy dissipation capacity.With the increase of PGA,the peak value of EPSD increases gradually,but the distribution shape does not change obviously.Finally,the probability density function and time-varying characteristics of the tower top responses under 34 random wave samples are analyzed.Based on the first-time failure criterion,the effect of random wave on the dynamic reliability of the wind power tower under different PGA was studied with the layer displacement as the control index.