| Wind power is a green energy resource. The utilization of wind power has extended from land to sea. The offshore wind power projects have been given full attention all over the world in recent years. As a key equipment to the construction of offshore wind farms,wind turbine installation ship (WTIS) is attracting more and more attention. Nowadays there are a lot of converted WTISs active in the construction of offshore wind farms all over the world. Since the converted WTIS subjects to different environment loads, the structural strength of WTIS has always been concerned in ship and ocean engineering area. Therefore this paper takes a WTIS which converted from a bulk carrier as research subject, and discusses the law of influence of the conversion design on the overall longitudinal strength and local strength, which aims to provide suggestions on WITS' structural strength research.At the beginning, the research background and significance of this paper are introduced, as well as the basic structural features of WTIS. Through survey, a review of the application and development of direct analysis method in ship structural strength area is given, which provides the research basis of this paper.In the next part, according to the structural features, the three-cargo-hold and whole-ship 3D FE models of the target ship are created, and the selection basis of boundary conditions is discussed. On this basis, together with rules of ABS and CCS, the different load types imposed upon the ship are given. Through comparative analysis, the appropriate calculation methods are determined. The number and distribution of each load type are given, as well as the way it applied.And next, based on the 3D FE models created above and FE theories, this paper studies the influence of conversion design on the overall longitudinal strength. The study focuses on the stern structures, and gives suggestions on the structural modification in that area.Moreover, comparative analysis between the results of three-cargo-hold model and whole-ship model is conducted, which summarizes their advantages and disadvantages, and gives the applicable conditions for three-cargo-hold model.Finally, this paper studies the influence of conversion design on the local strength. This part takes the conversion design of a typical structure, jib rack, as an example, analyzing the deck strength in that area. Then three improvement plans are provided. According to the local strength analysis results of the three plans, combined with economy, construction difficulty and other factors, the best plan is selected. |
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