Behavior of GFRP suction bucket in clay under ultimate limit state

Suction buckets fabricated from glass fibre-reinforced plastic (GFRP) have emerged as alternatives to conventional steel bucket foundations for offshore wind turbines. Numerical models incorporating a GFRP damage degradation model were developed to investigate the structural response of three critical GFRP bucket sections (S1: top transition, S2: mid-skirt, S3: bottom edge) under ultimate limit states. The results indicate that mechanical changes of the bucket skirt in section S1 are minimized, while the response of section S3 is maximized under different fibre orientations (f) and wall thicknesses (t). The maximum principal stress is minimized for f = 45°. The maximum deformation and ellipticity of the bucket skirt are 27 mm and 0.57 %, respectively, across different fibre orientations. The maximum principal stress and maximum circumferential strain show an obvious decreasing trend as the skirt wall thickness increases. When t ≥ 0.6 %D, the gap between the stresses and strains in each section of the bucket skirt decreases significantly. For varying wall thicknesses of the bucket foundation, the maximum deformation of section S3 are approximately 5.5 times that of sections S1. When the target reliabilities are 3.71, 4.26, and 4.75, the corresponding wall thicknesses of the bucket foundations are 0.259 %D, 0.265 %D, and 0.275 %D.