Surrogate Modelling Approach for Reliability-Based Design Optimization of a Semi-Taut Mooring System of a Floating Offshore Wind Turbine

Reducing the cost of floating offshore wind turbines (FOWTs) while ensuring safety remains a challenge. One promising approach is to optimize critical components, such as mooring systems, by balancing material efficiency with structural reliability. Reliability-Based Design Optimization (RBDO) offers a robust alternative to deterministic methods by incorporating uncertainties in material properties, manufacturing tolerances, and environmental conditions. This study focuses on optimizing mooring systems, where accounting for uncertainties in ultimate and fatigue limit states is crucial due to the high cost of mooring failures [1]. While frequency-domain models offer computational efficiency in early design stages, they often lead to conservative fatigue estimates and can under-predict mooring line tensions [2, 3, 4]. To improve accuracy, this study prioritizes time-domain simulations. However their high computational cost limits design space exploration. To address this, surrogate models are developed to accelerate limit state evaluations in the optimization process. This work outlines the implementation of two surrogate models: one for extreme loads and another for fatigue loads. A Design of Experiments (DoE) is generated using an automated evaluation framework, adapted from Yildirim et al. [5] for semi-taut moorings. This approach will identify key constraints, perform sensitivity analysis, and explore dimensionality reduction, enhancing the efficiency of the RBDO process for FOWT mooring systems.