Offshore Wind Turbines (OWT) are exposed to loads varying both in time and in amplitude, designating fatigue damage as a main concern. In this paper, an analysis is presented for assessing the total fatigue damage of an OWT tripod supporting structure. The combined effect of wind and wave loading is computed and different loading scenarios are examined to determine the dominating load on the final result. Further investigation is done to assess the influence of different welding profiles of the tubular joints of the structure on the final fatigue resistance. Results are presented and conclusions are drawn, indicating the importance of the combined analysis.
The geography of Greece consists of numerous inhabited smaller and bigger islands, with energy needs varying throughout the year. This decentralized demand for energy can be addressed by providing the islands with an autonomous source of energy production. Offshore Wind Turbines (OWT) are an appealing alternative to satisfy this need. A solution like this would allow the islands to use their own resources and produce their own energy in an environmentally friendly way. The realization of OWT is a complicated task and an engineering challenge. Several design scenarios have to be taken into account, including extreme load and fatigue load cases. OWT are exposed to critical environmental loads, which designate this kind of analysis essential. Contrary to common offshore structures- such as oil and gas platforms, OWT are not only exposed to dynamic wave loads but also to dynamic loads from the turning rotor of the Wind Turbine. These loads make OWT susceptible to fatigue damage. Loads varying in amplitude, direction and time act on the structure throughout its lifetime, progressively reducing the fatigue resistance. Deeper water depths for installation and turbines of larger size used nowadays, lead to increased loadings upon the supporting structure.
