Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Experimental Investigation on the Motion Response Characteristics of a Semi-Submersible Foundation
for Wind Turbines
Liudan Mao, Shaoming LiZhejiang Zhongyu Engineering Technology Co., Ltd.
Hangzhou, China

Zhipeng Zang, Fan Zhang, Shengquan Huang
School of Civil Engineering, Tianjin UniversityTianjin, China

ABSTRACTIn the deep sea areas far from the mainland, there are many highquality wind resources that can be developed and utilized. To developthese offshore wind farms with a water depth of more than 50 m,
floating-type foundations are often applied. The semi-submersible
foundation is one of the typical floating foundations for offshore windturbines. At present, many countries are actively developing thefoundations for offshore floating wind turbines, especially the semisubmersible foundations for wind turbines, and have made certain
progress in conceptual design, and researches on stability andhydrodynamic performances.

In this study, a series of physical model tests were carried out in athree-dimensional wave basin to investigate the motion response
characteristics and stability of a semi-submersible wind turbine
foundation under different waves, current and wind conditions. When
the waves and wind loads are superimposed, the maximum inclinationof the wind turbine foundation is slightly lower than that of the wave
load alone. When the wave, current and wind loads are combined, themaximum inclination of the wind turbine foundation is basically thesame as that of the wave load alone.

In terms of conceptual design, Bulder, et al. (2002) proposed a varietyof conceptual design schemes for floating foundations such as truncatedcone-shaped floating body, triangular platform and quadrilateralplatform. They comprehensively studied the feasibility of theseschemes in the water depth over 50 m from different aspects such as thestability, motion response characteristics, the usage amount of steel,maintainability, etc., which turns out that the triangular platform is theoptimal scheme. Zambrano, et al. (2006) installed three sets of windturbines on the semi-submersible platform MiniFloat, and used the time
domain analysis to study the motion response of the platform underdifferent working conditions. The result showed that the average pitch
angle was less than 5° and the amplitude was less than ±15°, indicatingthat the platform has good motion performance. Ishihara, et al. (2007)
designed a semi-submersible wind turbine platform that can carry threesets of wind turbine towers, and studied its motion response
characteristics under wave and wind loads through numericalsimulation and scale-model tests. Tang, et al. (2014) designed atriangular semi-submersible floating foundation for 5 MW wind turbine
and studied its hydrodynamic performance under different working
conditions. Deng, et al. (2016) proposed a conceptual design scheme ofa semi-submersible wind turbine platform based on a reinforced
concrete structure and carried out a performance analysis throughnumerical simulation, proving the feasibility of the scheme.

KEY WORDS: Semi-submersible foundation; wind turbine; motion
responses; environmental loads; physical model test.

NOMENCLATUREdH
Hs
LptT
Tp
Vp
Vmuv
γγ1/3γ1γ2γ3water depth, mwave height for regular wave, msignificant wave height for irregular wave, mcharacteristic line scale of the prototype, mtime, swave period for regular wave, swave period for irregular wave, scharacteristic speed of the prototype, m/scharacteristic speed of the model, m/scurrent velocity, m/swind speed, m/s
pitch angle, °1/3 maximum average value of the pitch angle forirregular wave, °pitch angle, °yaw angle, °rotation, °In terms of stability of the floating foundation, Musial, et al. (2003)pointed out that the oil platform must provide adequate stability toINTRODUCTION248