This thesis investigates some of the structural issues associated with the conversion of an oil tanker or a very large crude carrier (VLCC) into a floating production, storage, and offloading unit (FPSO). Specifically, a series of calculations were completed, including Finite Element Analysis (FEA), to evaluate the structural response of the stood interface of the topside module, resulting from its interaction with the FPSO’s hull girder in waves. The interfaces between topside modules and the hulls of converted tankers experience high fatigue loading. This loading, which is caused primarily by hull girder bending elongation in addition to inertia loading on the topside modules, creates a structural design challenge. A modern approach to solving a problem of such complexity requires the generation of a finite element (FE)model of the topside module, the stool interface, and the structure located immediately below the interface. The objective of this thesis was to determine a stool arrangement that performs the best in fatigue, while also meeting all class requirements for maximum allowable stress. The modeling and analysis of the so-called deck sub-model was carried out using the FEA program Sesam GeniE. GeniE is a program developed by Det Norske Veritas (DNV)Software that sees wide use in the industry for engineering and strength analysis of ships and offshore structures. The loading of the model represents the dynamic loads experienced by an actual FPSO concept or design. The FPSO concept was provided by an industry professional at Viking Systems, Lars Henriksen. A total of six different stool configurations were investigated in this thesis. Variables of consideration were: flexibility of connection points, sliding and welded connections, and number and placement of stools. In addition, the producibility challenges related to the stool design selection and integration, which is expected to impact the conversion cost.

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