Fatigue assessment of high-strength bolts with very large diameters in substructures for offshore wind turbines

Bolted connections in support structures for offshore wind turbines need to be thoroughly designed against fatigue damage. However, experimental validation of applicable fatigue curves for bolts with large diameters is limited. In this paper appropriate design methods are described. Results of experimental fatigue tests on high-strength bolts of size M36 are presented, including a quantification of the effect of different zinc coatings and the validation of relevant design S-N curves. The experimental results are further used for validation and discussion of first calculation results with a numerical fatigue calculation method, based on the notch-strain approach.