| Energy shortage has always been one of the main bottlenecks hindering the economic development in China.With the increasingly serious shortage of fossil energy and environmental pollution,changing the energy structure has become China’s long-term strategic goal.Therefore,China has gradually reduced the use of fossil energy such as coal,and vigorously developed all kinds of clean and renewable energy.As one of the most promising clean and renewable energy,wind energy includes onshore and offshore wind power.Among them,offshore wind power has attracted much attention because of its advantages such as high wind power density,stable wind speed and near to load center.Vigorously developing offshore wind power can greatly adjust the Chinese energy structure and alleviate the mismatch between energy distribution pattern and energy demand,contributing to the realization of green and sustainable development.In the Chinese 14th five-year plan,it is pointed out that in order to implement the"3060"goal,the scale of clean energy power generation including the offshore wind power will be vigorously improved.In 2021,the new installed capacity of offshore wind power in China is about three quarters of that in the world,and China has become the largest offshore wind power market.At this stage,the global offshore wind power development is moving from offshore to deep water,however,the offshore water depth is shallow in China.Therefore,floating offshore wind turbine in intermediate water depth is an important direction of offshore wind power development in China.The novel reinforced concrete semisubmersible floating platform,with inclined side columns for offshore wind turbine,while the stability,time-domain coupling dynamic response and strength analysis were carried out in this paper,so as to provide the experience for the safe,efficient and economic development of deep-sea wind energy in China in the future.The main research contents of this paper are as follows:1)Stability and frequency-domain hydrodynamic analysis of a conceptual semisubmersible floating platform.The numerical model of the semisubmersible floating platform was established using SESAM.Then,the effects of the central distance between columns,the inclination,diameter and freeboard height of the side columns on the intact stability for it were studied.Moreover,its main dimensions were adjusted,so as to make it more economical on the premise of meeting the intact and damaged stability,allowable vertical center of gravity（AVCG）and natural periods.Then the hydrodynamic model was established in Hydro D,and the hydrodynamic coefficients,first-order wave force transfer functions and response amplitude operators（RAOs）were calculated to reveal the ability of the structure to resist wave loads;2)Mooring design and dynamic characteristics of a conceptual semisubmersible floating platform in intermediate water depth.Based on the hydrodynamics of the platform,the design parameters of mooring systems and the control program of DTU 10 MW wind turbine,the time-domain coupled model was established in Sima to analyse the motion response under the conditions combined with wind and wave,at the same time,the effects of tidal level change,the pitch control system and the second-order nonlinear wave forces were considered;3)Strength analysis of the conceptual semisubmersible floating platform.The overall structures of the noval semisubmersible floating platform were designed.The design wave parameters corresponding to the different characteristic loads were obtained using SESAM,based on the long-term prediction.Then combined with the loads at the tower base under operating and extreme conditions,the internal force analysis of the floating foundation under the ultimate limit states were carried out to determine the internal force distribution and the most dangerous parts of the overall structure,which can provide conveniences for further detailed design and strength analysis. |
