Study on Multi-Scale Analysis of Large-Scale Floating Structure

近年来，为了实现建设海上机场的计划，大型浮式结构的研究开始活跃起来，这种大型浮式结构被称为Mega-float（或超大型浮式结构）。对于大型浮子结构的设计，需要对结构强度进行估算，但无法通过详细的有限元分析进行估算。在这方面，多尺度分析是一种有用的方法。在多尺度分析中，整体结构采用粗网格模型计算，细部结构采用细网格模型计算。为了提高缩放法求解的精度，本研究提出了叠加网格法。该方法将不同尺寸的网格进行叠加。局部网格表示详细的变形，全局网格表示粗糙的变形。两种网格的节点不需要一致，提高了生成分析模型的灵活性。为了使该方法适用于大型浮式结构的分析，本文从以下几个方面进行了改进。提出了壳固混合分析的叠加网格法。一般来说，像船舶和飞机这样的大型结构都是用壳和实体元素建模的。因此，这种改进的方法非常有用。并建立了裂纹扩展分析方法。这种方法不需要随着裂纹的扩大而重新建模。它使建模非常灵活。本研究的结果如下：首先，提高了精度。利用该方法可以方便地建立有限元模型。利用该分析方法，可以对船舶、大型浮子等大型结构进行精度高、灵活性好的结构分析。

Recently, the study of large-scale structure has become active, in order to realize the plan of constructing an offshore airport, which is called Mega-float (or the ultra-large floating structure). For designing of the big structure like Mega-float, it is necessary to estimate structural strength, but it is impossible to estimate using the detailed FEM analysis. In this respect, multi-scale analysis is useful method. In multi-scale analysis whole structure is calculated by coarse mesh model and detailed structure is by fine mesh.In this research, overlaying mesh method has been developed to improve the accuracy of the solution of zooming method. In this method, mesh with different size is superimposed. The local mesh represents detailed deformation and the global mesh represents rough one. The nodes of both meshes do not need to agree, which enhances the flexibility in generating analysis model. In order to use this method in analyzing the large-scale floating structure, improvements were made in following ways. Shell and solid mixed analysis of overlaying mesh method is developed. Generally, the big structures such as the ships and aircrafts are modeled of shell and solid elements. So, this improved method is very useful. And, crack growth analysis using this method is developed. This method does not require re-modeling as the crack grows. It makes modeling very flexible.The results of this study are as follows. First, improvement of the accuracy has been done. And, we can make the FEM models easily using this developed method. Using this analysis method, we can do the structural analysis of big structure such as ship and Mega-float with high accuracy and flexibility.