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Elastic Response Analysis of Very Large Floating Structures in Waves Using Spectrum Finite Element Method

波浪中超大型漂浮结构的弹性响应分析采用谱有限元法

基本信息

批准号：
08651102
负责人：
FUJIKUBO Masahiko
金额：
$ 1.47万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08651102/
关键词：
Very Large Floating Structure Finite element method Elatic response Beam model Response in Waves Bending response Torsional response 超大型浮体式海洋構造物曲げ振り応答超大型浮体式構造物メガフロート梁

项目摘要

The objective of the present project is to develop a simplified method of elastic response analysis of a Very Large Floating Structure (VLFS) in waves to evaluate the relationship between elastic response and structural parameters, such as mass and stiffness distributions, in the initial design stage. For this purpose, one-dimensional spectrum finite element using the dynamic shape function of bending and flexural-torsional deformation of a beam placed on an elastic foundation was derived. In the proposed approach, the exact solution of dynamic equilibrium equation of a beam under given extrernal loads can be obtained by small number of elements. The change in mass and stiffness can be easily considered by using standard finite element procedures.A series of structural response analysis of pontoon-type and semi-submersible type VLFSs was performed, and the influences of mass and stiffness distributions on structural responses were investigated. It has been found that :(1) The reduction of mass of the end part of structures is an effective way to avoid resonance in waves for pontoon-type very large floating structures.(2) The increase of bending stiffness is effective to reduce the bending response of a VLFS,including deflection and bending stress. The same holds for flexural-torsional responses.(3) The influence of vertical shear stiffness on the bending response of VLFS is only negligible.(4) For the VLFS with a large width to length ratio, the deformation as a plate takes place in width direction in reality. Accordingly, a beam model tends to overestimate the stiffness of structures.Some limitation must be therefore imposed on the application of a beam model to the response analyzes of a VLFS.

本项目的目的是开发一种简化的超大型浮动结构（VLFS）在波浪中的弹性响应分析方法，以评估弹性响应与结构参数（如质量和刚度分布）之间的关系，在初始设计阶段。为此，利用弹性基础上梁的弯曲和弯扭变形的动态形状函数，推导了一维谱有限元。在该方法中，只需少量的单元，即可得到给定外荷载作用下梁的动力平衡方程的精确解。质量和刚度的变化可以很容易地用标准有限元程序来考虑。对浮筒型和半潜式vlfs进行了一系列结构响应分析，研究了质量和刚度分布对结构响应的影响。研究发现：(1)对于浮桥型超大型浮体结构，减小结构端部质量是避免波浪共振的有效途径。(2)提高弯曲刚度可以有效降低VLFS的弯曲响应，包括挠度和弯曲应力。弯扭响应也是如此。(3)竖向剪切刚度对VLFS弯曲响应的影响可以忽略不计。(4)对于宽长比较大的VLFS，实际中作为板的变形主要发生在宽方向上。因此，梁模型往往会高估结构的刚度。因此，束模型在VLFS响应分析中的应用必须受到一定的限制。