SEISMIC RESPONSE ANALYSIS OF WIND POWER TOWER UNDER LONG PERIOD GROUND MOTIONS

The wind power generation has been widely used in the world. The number of wind farms built and under construction in seismically active areas is gradually increasing. Seismic loading has become an important factor in the design of wind turbines. In view of the dynamic characteristics of wind turbines, 20 far- and 20 near-field long period ground motions with rich of low frequency components were selected and seismic analyses of a typical wind turbine tower were performed with another 20 non-long-period ground motions as a reference. An OpenSees model was established for this 1.5 MW wind turbine using beam-column elements with fiber-sections and verified by the field measured data. On this basis, the seismic responses of the tower under long period earthquake were investigated, and the influences of the horizontal velocity pulse and the vertical seismic excitation of near-fault pulsed ground motions on the tower responses were discussed. Analysis results shown that the far-field ground motions induce more negative effects in the aspect of structural seismic responses. Under the same peak ground acceleration (PGA), the horizontal displacements at tower top and internal forces at the bottom of the tower due to ground excitation containing long period components are larger. The seismic responses of the tower under far-field ground motions with the PGA of 0.15 g were closed to that under the non-long-period ground motions with the PGA of 0.45 g. The vertical inertia force and P-Δ effects brought by the vertical seismic load increase the axial force and bending moment of the tower structure to a certain extent, but not obvious. The large PGA level is the main factor making the near-field pulsed ground motions more dangerous. Based on the fundamental frequency of the tower, two long-period ground motions were selected and scaled in order to analyze the plasticity of the cross-section. It is indicated that the cross-section at the height of 12 m yields firstly. When the peak ground acceleration reaches 0.5 g, the cross section enters of the tower plasticity, and when 0.6 g,it reaches yield.