Parametric Modellig and Fatigue Damage Assessment of Offshore Wind Turbine Support Structures

Abstract

Offshore wind turbines suffer a number of environmental loads which damage their support structure and decrease their lifetime. These forces are produced by the wind, waves and currents and they damage the monopile cyclically. This project aims to quantify that damage through simulating a parametric FEA (finite element analysis) and by applying Palmgren-Miner’s rule. For so, a model has been built in ANSYS Workbench and validated through a modal analysis. Then, the behaviour of a monopile in the Southern North Sea has been simulated: wind speed and wave height data were processed into applicable loads. From the results, the cumulative damage was calculated and lifetime defined. Finally, some parameters were altered to evaluate their influence on the fatigue damage. The parametric modelling and fatigue damage assessment showed, on the one hand, that cathodic protection for monopiles is indispensable and, on the other hand, that the use of larger (thicker, longer and bigger diameter) monopiles improves the lifetime of the structure as damage is reduced.