Fatigue reliability analysis of offshore wind turbines under combined wind-wave excitation via DPIM

TL;DR

This paper introduces a novel direct probability integral method (DPIM) for assessing the fatigue reliability of offshore wind turbine components under combined wind and wave excitations, validated against Monte Carlo simulations.

Contribution

The paper develops and validates a new DPIM approach for stochastic response and fatigue reliability analysis of floating offshore wind turbines under complex sea conditions.

Findings

Fatigue life under combined wind-wave excitation meets design standards.

Reliability is lower under aligned wind-wave conditions.

DPIM shows high accuracy and efficiency compared to Monte Carlo simulations.

Abstract

As offshore wind turbines develop into deepwater operations, accurately quantifying the impact of stochastic excitations in complex sea environments on offshore wind turbines and conducting structural fatigue reliability analysis has become challenging. In this paper, based on long-term wind-wave reanalysis data from a site in the South China Sea, a novel direct probability integral method (DPIM) is developed for the stochastic response and fatigue reliability analyses of the key components for the floating offshore wind turbine structures under combined wind-wave excitation. A 5MW floating offshore wind turbine is considered as the research object, and a fully coupled dynamic response analysis of the wind turbine system is conducted to calculate the short-term fatigue damage value of tower base and blade root. The DPIM is applied to calculate the fatigue reliability of the wind turbine structure. The accuracy and efficiency of the proposed method are validated by comparing the obtained results with those of Monte Carlo simulations. Furthermore, the results indicate that the fatigue life of floating offshore wind turbine structures under combined wind-wave excitation meets the design requirements. Notably, the fatigue reliability of the wind turbine under aligned wind-wave condition is lower compared to misaligned wind-wave condition.