Sicherheitsaspekte der Tragstruktur von Offshore-Windenergieanlagen

Safety aspects for support structures of offshore wind turbines

Offshore wind turbines (OWT) are subjected to loads induced by wind, sea and operation. During their life-time environmental varying impacts occur, which lead to cyclic loading of the support structure. Within the structural analysis of OWTs with jacket substructures, especially the proofs of the ultimate limit state for the axially-loaded foundation pile and for the grouted pile-in-sleeve connection between jacket and foundation pile (so-called grouted joints) are relevant.
In this paper the jacket substructure and the piled foundation of an OWT are investigated by applying probabilistic methods. The methodical approaches and procedures to determine the load-bearing capacity of the foundation are described. Input values for the environmental impacts of wind and sea are taken into account by their probability distributions. The stochastic pile bearing capacity is derived by applying probabilistic models. The result of the reliability-based analysis is compared to the structural analysis as stated in valid standards, and derived recommendations are given for the probabilistic design of offshore foundations.