Zonal coupling analysis method of seismic response of offshore monopile wind turbine

Offshore wind turbines are one of the important strategic choices for low-carbon sustainable energy, and their seismic safe-ty issues need to be solved urgently. In this paper, the three-dimensional seismic response problem of offshore monopile wind turbine is regarded as a wave scattering problem, and the fluctuation input of the sea site is realized by combining the artificial boundary conditions, and a set of efficient zoning analysis methods for seawater-saturated seabed-wind turbine coupling are developed based on the unified calculation framework of generalized saturated porous media, and the three-dimensional seismic response analysis of offshore monopile wind turbine is realized by comprehensively considering the soil-junction interaction effect and fluid-structure interaction effect. According to the data of the northeast sea area of Ru-dong Jiangsu, a 5MW wind turbine and site analysis model was established, and according to the seabed surface accelera-tion response spectrum obtained by the seismic safety assessment of the sea area, three seismic waves were selected from the NGA-West ground motion database, and the ground motion at the bedrock input was obtained through inversion, and the graded seismic response was analyzed. The effects of seawater depth, seabed wave velocity and seismic wave inci-dence angle on the seismic response of offshore monopile wind turbines were analyzed. The analysis results show that the changes of seawater depth and seabed shear wave velocity will change the free field on the one hand, and the self-vibration characteristics of the site-wind turbine system in the sea area on the other hand, thereby affecting the seismic re-sponse of the wind turbine structure. When the seawater increases to a certain depth, the seismic response of the wind tur-bine increases sharply when the self-resonance frequency of the system is close to the input frequency of the seismic wave. The seabed shear wave velocity has a greater influence on the bending moment at the bottom of the tower than on the displacement. When the incidence angle increases, the hori-zontal displacement and acceleration of the top of the tower and the bending moment at the bottom of the tower decrease to varying degrees, and the vertical displacement and acceleration of the top of the tower increase to different degrees. This paper does not consider the nonlinearity of the seabed and wind turbine, and the influence law of nonlinearity needs fur-ther study.