考虑设计规范的海洋平台结构选型优化

Layout optimization of offshore platform structures considering design rules

针对具体海洋环境条件和生产要求,对导管架平台结构进行选型优化——拓扑布局与构件尺寸的联合优化,充分考虑设计规范的要求,建立多设计准则、多约束条件和多荷载工况的设计模型,其中环境荷载包括:风、浪、流、海冰从不同方向对平台的作用。通过结构选型优化获得最佳的结构拓扑布局形式,在降低平台造价的同时,设计出满足结构的稳定特性、安全寿命等多种设计准则的新型平台结构。

Taking the CB11F offshore jacket platform that lies in the Shengli oil field as a case study, the theory and the application techniques of optimization design of offshore platform structures are investigated in this paper. The cross sectional sizes, nodal coordinates and layout of the structure were taken as design variables, a unified model for size, shape and topology optimization has been presented. As the coupling between various design variables causes trouble in dealing with the optimization problem, a two-level scheme is adopted to optimize the shape and size variables simultaneously. The ground structure method is used in topology optimization. The platform structure is under the action of multi-load cases including wind, current and floating ice from various directions. Based on the design regulations and rules, we consider various kinds of constraint conditions such as strength, stiffness, stability, etc. The optimization object is minimizing the weight of the platform structure. The Sequential Linear Programming (SLP) is selected to solve the optimization problem. In order to ensure the convergence of the iteration process, numerical approaches such as the adaptive move limit, the approximate line search and the approximate reanalysis have been proposed. JIFEX, a finite element analysis and optimum program package is utilized to implement the layout optimum design of the offshore platform, that generates a new platform model which satisfies various design requires such as the structural stability, safety service years, the lowest cost and so on. The topology-based optimized results were also compared with three different optimization levels under different load cases.