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

近年来，为实现建设海上机场的计划，对大型结构物的研究日趋活跃，称之为巨型浮体（或超大型浮体结构）。对于巨型浮体这样的大型结构物的设计，需要对结构强度进行估算，但采用详细的有限元分析是不可能的。在这方面，多尺度分析是有用的方法。在多尺度分析中，整体结构采用粗网格模型计算，细节结构采用细网格模型计算，本研究采用重叠网格法提高了缩放法的计算精度。在该方法中，不同尺寸的网格被叠加。局部网格表示细节变形，全局网格表示粗糙变形。两个网格的节点不需要一致，这增强了生成分析模型的灵活性。为了将该方法应用于大型浮体结构的分析，本文从以下几个方面进行了改进。发展了壳-体混合分析的叠加网格法。大型结构如舰船、飞机等一般采用壳单元和实体单元进行建模。因此，这种改进的方法是非常有用的。并利用该方法进行了裂纹扩展分析。该方法不需要随着裂纹的增长而重新建模。这使得建模非常灵活。本研究的结果如下。首先，提高了精度。而且，我们可以很容易地使有限元模型使用这种发展的方法。利用该分析方法，可以进行船舶、巨型浮体等大型结构的结构分析，具有较高的精度和灵活性。

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.