Comparative analysis and selection of structural types for deep-sea large-capacity wind turbine generator support frames

Abstract

This study systematically evaluates three-pile, four-pile, and five-pile jacket foundations for 11 MW wind turbines in about 50 m deep waters (Huadian Yangjiang Qingzhou 3 Offshore Wind Farm) using SACS software. Key performance metrics – static stress, pile head load, pile shaft moment/displacement, modal frequency, fatigue damage, seismic response, and steel quantity – were analyzed. Results show: (1) The four-pile jacket optimizes load distribution, reducing maximum pile head load by 33 % (vs. three-pile) and 14 % (vs. five-pile), with uniform axial/bending stress. Pile shafts exhibit “double-peak” bending moments (first peak at 15 m below mud surface) and displacement concentrated within 47 m of the mud surface. (2) First three natural frequencies (0.22–0.38 Hz) avoid resonance, dominated by tower stiffness. Fatigue damage increases with pile number (five-pile: 0.7243 > four-pile: 0.5305 > three-pile: 0.4862), with five-pile fatigue hard to control. Seismic action is non-dominant. (3) The four-pile jacket has the lowest steel weight (2054.33 tonne, 12.3 %/17.4 % less than three/five-pile) and unit cost. For deep-sea large-capacity wind projects, the four-pile jacket balances safety, economy, and constructability, serving as the optimal configuration.