Offshore wind energy is a global driver of the energy transition, with Europe playing a leading role. With this massive expansion, however, wind farms are increasingly advancing into tectonically active marine regions, a risk that also directly affects Europe due to earthquakes in the eastern Mediterranean, such as in Greece or Turkey. During operation, the turbine foundations must not only withstand millions of wind and wave load cycles, but also endure singular earthquakes that can trigger critical soil liquefaction. The OWICHEL project addresses this issue by investigating this interplay of natural forces to ensure the safety of future offshore wind farms under extreme multi-hazard loading conditions.

At the core of the investigations are realistic multi-hazard scenarios that go beyond the assessment of isolated single events. It will be analysed in detail how earthquakes affect structures whose foundations have already been subjected to years of wind and wave loads. Conversely, the research explores how wind turbines behave during long-term operation after a previous earthquake has destabilised the seabed. The effects of repeated earthquakes on structural stability over the entire lifecycle will also be simulated. 

The experimental investigations will take place on the uniaxial 1g shaking table at the Geotechnical Laboratory of Bauhaus-Universität Weimar. To realistically simulate the cyclic loads from wind and waves, the facility will be specifically equipped with a new electromechanical horizontal actuator for this project. Additionally, the existing instrumentation, which primarily consists of accelerometers, will be expanded with precise force and displacement sensors. With this setup, the 1g shaking table is capable of simulating the complex superposition of seismic ground motions and storm-induced environmental loads on scaled offshore wind turbines in the laboratory. For the foundation models, a scaling ratio of 1:100 is initially targeted, while further scaling approaches will be investigated over the course of the project.

For the numerical simulations, the geotechnical finite element program numgeo is used. In this framework, a high-cycle accumulation (HCA) model for the long-term environmental loads is combined with an innovative, mixed implicit-explicit (IMEX) time integration scheme for the transient earthquake phases. To validate the model, the 1g shaking table tests are first numerically simulated. Subsequently, full-scale practical examples are simulated to comprehensively analyse the structural behaviour of real offshore wind turbines under complex multi-hazard scenarios.

Further information on the DFG project OWiCHEL can be found here.

Project number: 579553772