Global Sensitivity Analysis of Offshore Wind Turbine Jacket

Nowadays, offshore wind turbine (OWT) energy is considered as one of the most promising among renewable energies. Many researches have been done to study offshore wind turbine foundations like jacket and monopile. The sensitivity analysis of the foundation can also be found in several researches. But there are always some limitations in these related studies. For example, the sea current is not considered and the directions of wind and wave are assumed to be aligned. The behavior of one specific element or part of jacket is studied. In this paper, the global sensitivity of the maximum stress and displacement with respect to material, local geometry and environmental uncertain parameters are investigated for the offshore wind turbine jacket used in Code Comparison Collaboration Continuation (OC4) project. Compared to other previous studies, the wind parameters are replaced by the load actions simulated in aerodynamic software FAST developed by National Renewable Energy Laboratory (NREL). The sea current is considered and the directions of the wind, sea wave and current are assumed to be independent. Also, the maximum stresses of static analysis in the different parts of jacket are investigated. The Morris screening and Fourier amplitude sensitivity test methods are applied to perform global sensitivity analysis. The results show that maximum stresses of different parts of jacket are affected by different parameters. The zones of the jacket above the mean sea level (MSL) are more sensitive to the geometry parameters and redefined wind loads. However, the zones below MSL are affected a lot by the wave parameters. In addition, the results of the two global sensitivity analyses are mostly in good agreement.