Basic research on dynamic safety of large offshore structure

本文对海上大型浮力构件结构的动力安全性进行了基础研究。促进我国海洋空间的有效、积极利用开发成为一个非常重要的问题。本文进行了循环水箱试验和计算机仿真分析。本研究得到的主要结果总结如下：1)各柱涡激振动受柱构件间距的影响。对于旋涡激振的响应，在单柱情况下，随着柱间距的缩小，旋涡激振的响应呈增大趋势。此外，已经了解到，由于频率的差异，整个结构的扭转振动是由前后柱的涡激振动产生的。2)如果将结构在波浪力和地震力分别作用下的反应进行比较，由于这些外力作用的位置不同，结构的弯矩应力差异较大。然而，据了解，当结构扩大时，在与连接材料结合的结构模型中显示出类似的响应。3)采用波浪力可靠度指标和地震力可靠度指标对设计水平响应进行比较。在波浪力中，平均波高、平均波周期和持续时间是主要参数。地震力的主要参数是加速度和表面层的主频率。利用可靠度指标对具有完全不同动力特性的外力进行响应评价，并评价各外力的影响是有益的。4)当结构恢复力特性变为线性和非线性时，海上结构在波浪力作用下的最大响应依赖很大。特别是对长持续时间波浪力的最大响应理解非线性特性的影响较大。因此，在评价设计水平响应时，弄清其影响是十分重要的。少

A fundamental examination concerning dynamic safety of large offshore structure with buoyancy members was done in this research. Advancing an effective, positive use development of an oceanic space in our country becomes a very important problem. The circulating water tank experiment and the simulation analysis by the computer are done in this research.The main result of obtaining for this research is summarized as follows.1) Vortex induced vibration in each column is influenced by the interval of column member. As for the response by vortex induced vibration, the increasing tendency was seen at the case of single column when the interval of column narrowed. Moreover, it has been understood to cause torsion vibration as the entire structure by the difference of frequency where the vortex induced vibration of column in the back and forth is generated.2) If the responses of the structure subjected to separately wave force and seismic force were compared, a big difference was shown in ben … More ding moment stress because the position where these external force acted was different. However, it has been understood to show-a similar response in the structural model which is united with connected material when the structure is enlarged.3) The comparison on the design level response is done by using the reliability index for the wave force and the seismic force. In wave force, mean wave height, mean wave period, and duration are the main parameters. Moreover, the main parameter of seismic force is dominant frequency of the acceleration and surface layer. It has been understood that it is useful to be able to do the response evaluation to external force with a quite different dynamic characteristic by using the reliability index, and to evaluate the influence of each external force.4) The maximum response of offshore structure subjected to wave force depends greatly when the restoring force characteristic of the structure becomes linear and nonlinear. Especially, the maximum response to wave force with long duration understands the influence of a nonlinear characteristic is large. Therefore, it is important to clarify the influence in the evaluation of the design level response. Less