Structure Design And Mechanical Analysis On The Pressure Balanced Buoyancy Supported Risers Platform Of FPSO

Because the enormous increasing energy consumptions in the 21 st century, the deep oil and gas development has been being the trend of The Times. Floating Production Storage and Offloading vessels(FPSO) are more widely used in deep-water offshore engineering. CoMPared to the shallow water, Buoyancy Supported Risers(BSR) are installed in the two to three hundred meters underwater, to reduce the tensile strength between the turret structure of FPSO and the deep-sea risers, resulting of significant increase in the length of deep-sea risers. In order to improve the complex launching operations and the time-consuming installation of the existing BSR, this paper designed an innovative structural form of the Pressure Balanced Buoyancy Supported Risers Platform and its internal pressure-resisting pontoons, which can realize one-time erection and overcome that shortage very well. And structure performances of pressure-resisting pontoons are analyzed.The first chapter mainly introduces the research background and significance of this paper. After analyzing the research status at home and abroad, the direction and approaches are put forward for the paper.The second chapter designs the Pressure Balanced Buoyancy Supported Risers Platform, improving the launching principle of the existing floating platform. The main structures of the innovative platform stand with no pressure, equipped with pressure-resisting pontoons inside which can realize the one-time underwater installation. Then, the structure parameters of the platform and its pressure-resisting pontoons withstanding uniform internal pressure are designed completely.The third chapter changes the load form of the pressure-resisting pontoons to external pressure, then analyzes the structure performances of the pontoon subsections withstanding external pressure, on the basis "the diving system and submersible rules for the classification and construction" of China Classification Society. The structural parameters of the pontoon subsections withstanding external pressure are designed and optimized based on the polynomial response surface functions fitting the stresses in the CCS Rules. CoMPared to the pontoons withstanding uniform internal pressure, the pontoons withstanding uniform external pressure are more superior design schemes, which are lighter and need smaller steel yield strength.The fourth chapter based on the direct design approach, in according to the parameters of pontoons subsections withstanding uniform external pressure designed by the CCS Rules, discusses the influence between the nonlinear stability of pontoon subsections and four parameters, such as shell thickness, steel yield strength and tee bar and rib intervals. Further optimization and analysis is done by using the finite element models.The fifth chapter is summary of the paper, and points out the direction of future work.