Proposal for the suitable choice of material to avoid brittle fracture on Jacket foundations

In the past years offshore wind turbines have been established as a source of renewable energies. Especially installations at greater distances from the shore and thus at increasing sea depths offer great potential. The foundations of these structures are exposed to complex load configurations while simultaneously exhibiting difficult environmental conditions. Although, there are currently no harmonized regulations with regard to the suitable choice of material to avoid brittle fracture for the hollow section joint structure of a Jacket foundation. In accordance with EN 1993‐1‐10 appropriate rules are given in terms of onshore structural engineering. Although, due to the differing conditions, these rules can not be applied to offshore foundations without further modifications. To achieve a suitable application, investigations regarding the material toughness requirements for Jacket foundations of offshore wind turbines were carried out. A parametric study regarding stress concentration was conducted to identify a reference geometry. Afterwards a fracture mechanics approach was applied to define the material toughness requirements. The obtained results served as a basis upon which a proposal to avoid brittle fracture for Jacket foundations was drafted.