Structural integrity assessment of fixed support structures for offshore wind turbines: A review

Abstract

The objective of the present study is to provide a review of the structural integrity of fixed support structures for offshore wind turbines, focusing on the physics behind the failure mechanism to assess the structural integrity. It covers the historical background of the fatigue and fracture phenomena, physics-based modelling techniques, methods to estimate the extent of the crack and its criticality, and finally, different models to predict the remaining life of the support structures in-service. The methodologies used for the fatigue design and the damage-tolerant maintenance planning of the offshore wind turbine support structures have benefited immensely from the experience and know-how gained from the onshore wind and offshore oil & gas industries. Thus, the present paper also reviews those studies which have been influential for both structural integrity and structural reliability of offshore wind turbine support structures, which is essential for the remaining life estimation and life-cycle management decisions. Furthermore, a risk-based framework for a structural integrity assessment is discussed considering the uncertainties involved in the numerical and analytical modelling, loads, structural response, and material properties, leading to building quantitative models to predict the impact of different actions on structural conditions and economic liabilities from a strategic perspective.