Analytical solution of dynamic responses of offshore wind turbine supported by monopile under combined earthquake, wave and wind

Abstract

Offshore wind turbine system (OWTs) in areas of earthquake activity are potentially threatened by a combination of earthquake, wave, and wind loads. Thus, an analytical solution of OWTs supported by monopile on viscoelastic half-space is developed to investigate the dynamic responses of OWTs subjected to the earthquake, wave, and wind loads. Firstly, the OWTs supported by monopile considering a series of coupled interactions is established, in which monopile end soil-soil viscoelastic half-space interaction is solved by static spring-damping system, monopile-soil and water interaction are solved by analytical horizontal impedance, monopile-wave interaction is solved by linear wave theory, and tower drum-wind interaction is solved by wind loads applied on the turbine blades. Then, the displacement response of OWTs supported by monopile is further obtained based on the continuity conditions between the monopile and tower drum. Finally, the present solution degenerated into a rigid foundation and verified the rationality with existing analytical and substructure methods. In addition, some critical parameters are further conducted by using the present solution. The results indicate that it is necessary to consider the couple influence of earthquake, wave, and wind loads in the design of OWTs supported by monopile.