Dynamic response of jacket-supported offshore wind turbines subjected to obliquely incident SV and Rayleigh waves

This study investigates the seismic response of jacket-supported offshore wind turbines subjected to obliquely incident SV and Rayleigh waves, considering dynamic soil–structure interaction (SSI). The analysis is conducted using the OpenFAST numerical framework, extended with an SSI model to represent the dynamic impedance of pile foundations. Additionally, the tool was adapted to account for the non-synchronous excitation at the different supports that arises from the arrival of obliquely incident planar waves or surface waves. This has allowed studying the response of the system under waves that shake the structure in different directions, and that, in the case of SV waves, reach the site with a wide range of angles of incidence, from vertically-incident to sub-critical incidence. It is shown that restricting the seismic response analysis of this type of structures solely to vertically incident ground motions may result in an underestimation of the total structural demand. In particular, the amplification of peak internal forces under obliquely incident SV waves indicates that kinematic interaction plays a key role in obtaining an accurate estimation of structural demands. Furthermore, the maximum internal forces induced by Rayleigh waves tend to be higher than the forces induced by vertical shear waves for the same record.