Research on fatigue damage mitigation of offshore wind turbines by a bi-directional PSTMD under stochastic wind-wave actions

Abstract

In view of an especial frequency tuning pattern, a prestressed tuned mass damper (PSTMD) with a larger mode damping has been proposed and explored its vibration control competence for offshore wind turbine (OWT). Unlike the vibration control research under a certainly given wind-wave actions, the fatigue damage of OWT structure is directly associated with the stochastic and complex environment correlation variables in real offshore site. This paper further develops the bi-directional PSTMD to mitigate the fatigue damage of OWT structure subjected to stochastic wind-wave actions. The mathematical models of OWT and bi-directional PSTMD are established to deduce the fatigue stress, and the aerodynamic and hydrodynamic loads from stochastic wind-wave actions. Some met-ocean data are used to study the stochastic probability distribution, and build the joint probabilistic density functions from various environmental factors. The Rain-flow Counting, S-N curve and Miner’s rule algorithms are used to comparatively explore the fatigue damage mitigation of bi-directional PSTMD under the stochastic wind-wave actions. The results show that this bi-directional PSTMD can mitigate the fatigue damage over 53.73% and 54.95% compared with the conventional pendulum TMD (PTMD) at the tower-base and seabed cross sections respectively.