Abstract:
Wind power, especially offshore, is considered to be one of the most promising
sources of ‘clean’ energy towards meeting the EU targets for 2020 and 2050.
However, its popularity has always fluctuated with the price of fossil fuels since
nowadays wind electricity production cannot compete with nuclear or coal
electricity production. Support structures are thought to be one of the main drivers
for reducing costs in order to make the wind industry more economically efficient.
Foundations and towers should be fit for purpose, extending their effective
service life but avoiding costs of oversizing.
An exhaustive review of the background and state of the art of the Fatigue-Life
assessment approaches has been carried out, combining analysis of the
gathered experimental data and the development of Finite Element models based
on contemporary 3D solid models with diverse Regression Analyses, in order to
identify their weakness and evaluate their accuracy. This research shows that the
guides and practices currently employed in the design and during the operation
of the offshore wind turbine support structures are obsolete and not useful for
optimisation, which generally leads to conservationism and an unnecessary
increase in costs.
The basis for a comprehensive update of the Girth Weld and Tubular Joint S-N
curves and the Stress Concentration Factors of Tubular Joints has been set out.
Furthermore, a reliable methodology for deriving the Stress Intensity Factor at the
deepest point of a semi-elliptical surface saddle crack in a tubular welded T-joint
has been proposed.
