Probabilistic calibration of fatigue safety factors for offshore wind turbine concrete structures

Current fatigue design rules for offshore concrete structures were adopted from the oil and gas industry. When better models or more information are available, partial safety factors can be re-calibrated according to target reliability levels for offshore wind turbines. This paper describes a framework for reliability-based calibration of fatigue partial safety factors for offshore wind turbine concrete structures. Offshore wind turbine loads accounting for the statistical distribution of turbulence intensity are estimated using a fully-integrated aeroelastic model. Based on available experimental fatigue tests, a fatigue reliability model for concrete is formulated and applied in two numerical examples. Results indicate that the recommended material partial safety factor in the DNV standard for Offshore Concrete Structures can be lowered without compromising structural safety. The proposed modification can potentially contribute to structural design optimization and further cost reduction in offshore wind energy.