Some floating production, storage, and offloading units (FPSOs) possess disconnectable systems to avoid harsh environments. According to a literature survey, the practice is based on perceptions and experiences of operators to judge disconnection; however, this paper offers a rational approach. A life-cycle cost model is proposed to optimize (1) the disconnection criteria and (2) the design of mooring lines under reliability format. Relevant ultimate limit states are considered in association with hull, moorings and green water failure. Effects of future failure costs is considered (downtime, environmental damage, reputation, etc.). Disconnection criteria are then formulated in terms of significant wave height and wind speed limits. Because a permanent mooring system may exhibit excessive resistance, it is possible to reduce the lines' thickness until the cost is optimized for non-permanent service. Results for an example in the Gulf of Mexico show that important savings can be achieved by implementing the proposed optimizations.
Agradeço aos meus pais e irmão pelo constante incentivo e apoio ao longo de minha vida.Ao meu orientador, Prof. Dr. Celso Kazuyuki Morooka, pela oportunidade concedida e a orientação durante a realização deste trabalho.Aos prezados professores participantes da banca deste trabalho, pela paciência e disponibilidade para leitura desta dissertação, bem como pelas valiosas sugestões e críticas construtivas dadas à autora.
The main purpose of this work is to study a two dimensional coupled analysis, in vertical and lateral directions, of the dynamic behavior of a seawater intake riser (SWIR). The dynamic solution is performed in time domain, through the time integration Newmark-beta method, and the use of the Newton Raphson method to solve the nonlinearity problem. A finite element computational method is deployed to have a better understanding of the vertical motion contribution in the overall system, taking into account the environmental loads (wave) and the heave motion of the FLNG vessel.
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