Dynamic Analysis of a Tripod Offshore Wind Turbine under Earthquakes

Earthquakes are non-negligible hazards for the designing of offshore wind farms in the coastal regions of China, such as Bohai Bay. So, it is necessary to analyze the response of offshore wind turbines (OWTs) under earthquakes. Fluid mechanics are applied to the model, the interactions of sea water and the substructure are based on fluid theory analysis in this paper. Moreover, it takes into account of the influence of fluid-solid coupling effect, radiation effect of wave loads and pile-soil interactions on the OWT. By establishing the finite element model (FEM) and dynamic equation of a tripod OWT, the measured onshore and offshore seismic waves are applied in the finite element analysis of the Tripod OWT respectively, and the numerical analysis of a tripod OWT structure under different measured seismic waves is carried out. More detailed comparison of the differences between onshore and offshore seismic waves is carried out in the paper. The result shows that the offshore seismic waves stimulate more significant responses than the onshore one, which can be attributed to that abundant seismic frequencies are found around the fundamental frequencies of the OWT. the seismic response analysis is conservative by using the onshore seismic waves, however, using the offshore seismic waves is closer to the actual situation.