Flexible Riser Static Configuration Analysis And Bend Stiffener Design

In modern offshore oil industry, the deep-sea oil production has become the mainstream. With the increase depth of platforms and FPSO, marine flexible riser, known for its good adaptability to the deep-water environment, has been widely used. Due to the configuration of the deep water flexible risers lack of practical engineering experience, effective configuration parameters are absence, its morphology brief analysis of becomes very important. In the use process of the flexible riser, since the stiffness of the riser and platform at the connection is not continuous, it is easy to occur stress concentration and excessive bending phenomenon here, the installation of bend stiffener can prevent this phenomenon, and ensure the safe and efficient production of platform. Bending stiffener is an important part of the overall structure of the riser, but so far, the domestic has not made a research on structural design of bend stiffener.In this paper, lumped-mass method is used for static analysis of flexible risers. The typical lumped mass has been model modified, with the bending moment is translated into the internal force that is applied to the node, so it can consider the bending effects during the process of deformation of the flexible risers. With the catenary theory between the flexible risers boundary conditions and boundary value, the process will get the boundary value conditions from the displacement boundary conditions. Using this model to analysis catenary flexible riser and the flexible jumper in static, it is found that the lateral displacement is restricted after considering the overall flexural rigidity of the structure, the bending moment of the unit is reduced, the same as in the suspension tension and suspension angle case, the tension inside the unit is reduced. But this effect is not obvious.The bend stiffener of flexible risers is also analyzed. Bend stiffener design, based on evolutionary strategy optimization algorithm, to finding the structure that is compliance with the structural design requirements and the deformation is reasonable; at the same time to minimize its volume. In the optimization process, the sensitivity analysis of geometric parameters of the bend stiffener has been done firstly. With the qualitative analysis of the impact of the geometric parameters on the anti-bending effect, it identified the geometric parameters that have a greater impact to be the main parameters of the structural optimization. Then to modify the classic evolutionary strategy and determine this article optimizer process. The fitness function is also determined; it should be included anti-bending volume, the maximum curvature and the position of the maximum curvature. Finally, using slender beam model to simulate a combination structure of flexible risers and bend stiffener to check the optimized result.Through comparison of the optimization results and literature, it is found optimization result of geometric parameters in this optimization procedure and classic bend stiffener is approximate. The numerical convergence and stability is better.it shows that the calculation result of optimization program is reliable; it can seek for optimal solution in a certain range. The effect of optimization is better, and it is better than the traditional genetic algorithm.