Integrated soil–structure model for seismic analysis of jacket-based offshore wind turbines

Abstract

This paper presents a boundary element–finite element model for the seismic analysis of jacket-based Offshore Wind Turbines (OWTs). Unlike traditional substructuring methods that rely on simplified spring-based foundations, this study proposes an elastodynamic formulation in the frequency domain that treats the structure and the soil as a single coupled system. By using Green’s functions for a layered viscoelastic half-space, this model captures the full spatial nature of seismic excitation and energy radiation without requiring soil mesh discretization. This direct approach provides an advanced and natural representation of Soil–Structure Interaction (SSI). A comparative study is performed to evaluate the response of OWTs using the proposed model against fixed base and simplified engineering SSI approaches. The study assesses three- and four-legged jackets at both 20 m and 50 m water depths, using pile and suction caisson foundations in homogeneous and non-homogeneous soils. The results quantify SSI effects such as the reduction of natural frequencies and the increase in system damping. Findings indicate that while simplified spring-dashpot models from existing literature are easy to incorporate, they can be unreliable for complex configurations. This emphasizes that a direct approach is essential for robust seismic design and analysis of multi-supported offshore wind structures.