圆筒型FPSO上部模块支撑结构疲劳分析

与船型FPSO相比，圆筒型FPSO没有明显的总纵弯曲，上部模块与船体结构之间通常采用刚性支墩来连接，水平运动所产生的弯矩和装/卸载引起的船体垂向变形对模块支撑结构的影响较为显著。因此，以“希望6号”圆筒型FPSO上部模块支撑结构为研究对象，基于DNVGL船级社规范，介绍一种简化疲劳分析方法。以FPSO运动加速度和船体变形载荷作为载荷输入条件，利用SESAM/GeniE软件进行有限元分析，得到结构在所有组合工况下应力的扫描计算结果。根据作业海域各个方向波浪发生的概率，运用简化疲劳分析方法计算得到所关注节点的疲劳损伤和各个工况对结构节点疲劳损伤度的贡献。结果表明，所关注节点的疲劳强度均满足设计疲劳强度要求；同一节点的疲劳损伤对不同浪向的敏感度不一样。该简化疲劳分析方法同样适用于承受周期性载荷的FPSO上部模块主结构和其他型式海洋结构物的疲劳分析。

Fatigue Analysis for Topside Module Supporting Structure of Cylindrical FPSO

There is no obvious longitudinal bending for cylindrical FPSO as compared with ship shaped FPSO, rigid stools are usually used to connect the topside modules and hull structure, the bending moment caused by horizontal motion and the vertical deformation due to loading/offloading have a significant impact on topside modules supporting structure. Therefore, taking the topside modules supporting structure of cylindrical FPSO as research object, a simplified fatigue analysis method is introduced based on DNVGL Rules and Standards. The motion accelerations and hull deformation loads are used as input load, the Finite Element Analysis is carried out using SESAM/GeniE, and the scanned results for structural stress for all combined load cases are calculated. The fatigue damage of the concerned structural joints and the contribution to fatigue damage for different wave conditions can be obtained by using the simplified fatigue analysis method, based on the heading probability of wave in operation waters. The results show that the fatigue strength of the concerned joints meets the requirements for the design fatigue strength, and the sensitivity of fatigue damage to different wave directions is different for the same structural joints. This simplified fatigue analysis methods are available for fatigue assessment of topside module primary structure and others type of offshore structures which subject to cyclic load.