Application of bidirectional fluid-structure interaction modelling to offshore systems

The biggest problem of today's world is energy supply. It is the most important determinant of international competition and economy. Offshore structures are capable of responding to this need. In order to extract consumable resources such as oil and natural gas, and to benefit from wind energy, the orientation towards offshore structures has increased. The decrease in land costs and land reserves caused the platform cage system constructions to shift towards the sea. According to the connection types of platforms with the sea surface; It can be divided into different sections as fixed, strut and floating types. In this thesis, two different cage-type platforms, fixed to the seabed, three different models, one three-legged and one four-legged, were designed using the ABAQUS finite elements method. Solid models were designed using the ABAQUS/Explicit solver, while fluid models were designed in the ABAQUS/Cae section of the program, and subjected to wind and wave loads. In this study, a section of supporting profiles was removed from one section of the designed four-legged model. The results were compared with the other two models under similar conditions, subjected to the same exposure, and the results were obtained. Offshore structures can occasionally be damaged during ship docking or commercial passages. Such a scenario assumes that one of platforms maintains its service performance after the profile is lost. The results were compared using program analysis and manual verification, and platforms deformation and stress values over time were compared. The mode shapes, maximum stress and displacement values related to the naturel frequency values of the structures were investigated. In addition to the structural outputs, the wave forces acting on the structure along with the wave free surface motion were obtained semi-analically and numerically and the numerical analysis were verified.