Seismic response of monopile-supported offshore wind turbines embedded in different seabed profiles including dynamic soil-structure interaction.

Abstract

Due to offshore wind power energy expansion in recent years, seismic analysis of offshore wind turbines (OWTs) has become a relevant factor to consider. Recent recommended practices (such as DNV-RP-0585 “Seismic design of wind power plants” [1]) and many earthquake studies have been published recently. Although most of these works are focused on analysing the effects of soil-structure interaction (SSI, e.g. [2, 3]), other aspects such as the seabed profile typology on which they are founded, or the influence of kinematic interaction (KI) within SSI on the seismic response of this type of structures, have not yet been addressed in detail. For this reason, this work aims to study the seismic structural response of four monopile supported OWTs embedded in different seabed profiles, including SSI effects and analysing KI contribution on it. The effects of the soil profile on the seismic response are studied by considering one homogeneous and two non-homogeneous soil profiles with equivalent shear-wave velocities. The system response is quantified in terms of maximum bending moments and acceleration amplification factors, which are computed by using a finite element substructuring model in frequency domain, the foundation behaviour is obtained by a continuum model including kinematic and inertial interaction. The results show that the differences between homogenous and variable-with-depth soils arise mainly from the rotational KI factor. However, the largest¡ responses are obtained when SSI effects and the equivalent homogeneous soil profile are considered, justifying the use of homogeneous soils in the initial design stages of this type of structures.