Hydrodynamic analysis of semi-submersible offshore structures has been the topic of several numerical and experimental research studies conducted in the past. In this work, the effect of structure alignment and mooring lines on the dynamic behaviour of semi-submersible platforms was taken into account. The contribution of pitch and roll into heave motion of side-points was also investigated. Mooring lines are connected to semi-submersible platforms at the sides; therefore, the total displacement of side-points is related to the total displacement of mooring lines and total tension. A three-dimensional boundary element model of Amirkabir platform in the Caspian Sea was created using the boundary element method and the resulting response amplitude operators (RAOs) were obtained. A conceptual study on RAOs was conducted, which showed that structure alignment with respect to wave direction is highly important for a range of wave periods. In addition, in surge and sway, the effect of mooring lines is significant in particular ranges of wave periods. The contributions of roll and pitch to the side-points of semi-submersible platforms are also considerable in a range of periods.

中文翻译：

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半潜式平台动力响应概念研究

半潜式海上结构的流体动力学分析一直是过去进行的多项数值和实验研究的主题。在这项工作中，考虑了结构对齐和系泊缆绳对半潜式平台动态行为的影响。还研究了俯仰和横摇对侧点起伏运动的贡献。系泊缆与两侧的半潜式平台相连；因此，侧点的总位移与系泊线的总位移和总张力有关。利用边界元法建立了里海Amirkabir平台的三维边界元模型，得到了响应幅值算子（RAOs）。对 RAO 进行了概念性研究，这表明相对于波浪方向的结构对齐对于一系列波浪周期非常重要。此外，在浪涌和摇摆中，系泊缆绳的影响在波浪周期的特定范围内是显着的。横摇和俯仰对半潜式平台侧点的贡献在一定时期内也相当可观。