The need for fossil fuels and hydrocarbons is increasing as the population grows. On the other hand, with the reduction of fossil resources due to its over-exploitation on land and in the shallow sea, researchers have turned to the deep sea and extract resources in its bed. Extraction of resources in the deep sea requires the use of modern offshore platforms that, in addition to operating in deep water, are capable of withstanding adverse sea conditions. One type of offshore platform that performs well in deep water and performs well under acute environmental conditions is the semi-submersible platform. The semi-submerged platform is a floating structure in which the environmental forces embedded in it cause movements. The movements created also affect drilling and extraction operations. Therefore, analysing the movements of the platform is of particular importance.
In this thesis, the GVA4000 half-submersible platform is chosen as the model. Hydrodynamic simulation and analysis of this platform were performed in Ansys Aqua software using the boundary element method. The purpose of this study is to investigate two important challenges in the geometry of the semi-submerged platform. The first challenge concerns the change in the vertical positioning of the semi-submersible platform brace, which is analysed in six different positions. And the second challenge is the change in the diameter of the semi-submersible platform brace, which is examined in six different diameters. At all these stages, the waves hit the semi-submerged platform at an angle of 180 degrees. The rao heave and pitch and surge in all modes in the frequency domain. For validation, the results of numerical analysis of this platform, in diameter D and height of brace H, are compared with the experimental results performed by Abyn et al. The investigations show the high accuracy of the boundary element method used in this study. The results of this thesis show that as the diameter of the half-submersibl