Structural Collapse Behavior of Very Large Floating Structures in Waves

提出了一种浮箱式超大型浮式结构物在波浪中整体倒塌分析方法，并将其应用于超大型浮式结构物在极端波浪中的结构安全性评估。结果可以总结如下1。作为超大型浮体结构失稳分析的基本工具，开发了理想结构单元法（ISUM）加筋板屈曲/塑性失稳分析的计算机程序。ISUM中所需的自由度（d.o.f.s）远小于有限元分析（FEA）。通过与有限元分析结果的对比，验证了ISUM分析结果的正确性.采用ISUM加筋板模型，编制了VLFS连续倒塌分析程序。引入ISUM超元概念，进一步减少了待求解的自由度，实现了对平面尺寸为数千米的超大型浮体的整体倒塌分析.为了研究超大型浮体在波浪作用下动力倒塌的基本特征，采用弹性本征模态之和表示的挠度，对超大型浮体进行了简化的动力倒塌分析。进行了小比例模型的水槽试验，以检查项目中采用的水弹性响应分析的准确性4。将ISUM和弹性响应分析相结合，建立了浮箱式超大型浮体结构在波浪中的整体倒塌分析系统。将水弹性响应分析得到的包括辐射力在内的外荷载准静态地施加到安装在弹性地基上的ISUM VLFS模型上.应用该系统对某浮动机场模型在极限强度状态下的结构安全性进行了评估。结果表明，超大型浮体结构在设计荷载以外有足够的强度储备。并对考虑防波堤损伤的浮箱型VLFS结构进行了可靠度分析。

A method of global collapse analysis of a pontoon type Very Large Floating Structure (VLFS) in waves was developed and applied to the structural safety assessment of a VLFS in extreme waves. The results can be summarized as follows1. As a fundamental tool of the collapse analysis of a VLFS, a computer code for the buckling/plastic collapse analysis of stiffened plates using Idealized Structural Unit Method (ISUM) was developed. The degrees of freedom (d.o.f.s) required in ISUM is much smaller than in Finite Element Analysis (FEA). ISUM results were verified through a comparison with FEA results.2. A computer code for the progressive collapse analysis of a VLFS was developed applying ISUM stiffened plate model. A concept of ISUM super element that can further reduce d.o.f.s to be solved were introduced to enable a global collapse analysis of a VLFS having planar dimensions of thousands of meters.3. In order to examine the fundamental features of dynamic collapse behaviour of a VLFS in waves, a simplified dynamic collapse analysis of a VLFS was performed assuming the deflection expressed by the sum of elastic eigen modes. A tank test for a small-scale model was performed to examine the accuracy of hydroelastic response analysis employed in the project4. A system of global collapse analysis of a pontoon type VLFS in waves was developed combining ISUM and elastic response analysis. The external loads including radiation forces, obtained by the hydroelastic response analysis, are applied quasi statically to ISUM VLFS model mounted on an elastic foundation.5. Applying the developed system, the structural safety of a floating airport model in ultimate strength limit state was assessed. It was found the VLFS under consideration has enough strength reserve beyond the design loads. The structural reliability analysis of a pontoon-type VLFS considering damage to the breakwater was performed also.