A Study on Structural Standardization of Connections of Floating Offshore Structure

根据实际半潜式船体连接处结构加固的调查结果，对两种情况进行了研究；一种支撑直接焊接于柱外表面的情况和支撑穿透柱壳壁的情况。另一方面，根据实际半潜船在设计波作用下的分析结果，提出了12种基本荷载模式，通过这些基本荷载模式的线性叠加来表达连接的荷载条件。同时也证实了支撑的外力在连接结构强度中占主导地位。因此，在本研究中，轴向力主要用于支撑。采用几种小比例尺亚克力模型进行了试验，并进行了有限元计算，探讨了连接内配筋构件之间荷载的传递机理。第三次研究表明，从应力流动和重量最小化的角度来看，支撑穿过柱壳墙并由水平图支撑的情况是最有效的。通过小比例尺模型试验和不同配筋构件的有限元计算，研究了不同配筋构件的屈曲-倒塌强度。研究结果表明，具有支撑贯通和水平图或环梁内支承构件的连接具有较高的抗屈曲破坏能力。后一种情况下，环梁腹板面板的选择和跳闸托架的合理配置至关重要。采用大型和小型钢模型进行了疲劳试验。结果表明，上述加固方法具有较高的抗疲劳性能。此外，还讨论了裂纹萌生寿命、贯穿厚度寿命和失效寿命作为复杂配筋试件情况的一般方面的意义。

Based on results of survey of structural reinforcements at connections of actual semisub- mersibles, two cases were inverstigated in this study; a case wher a brace is directly welded to outer surface of column and a case where a brace penetrates a column shell wall.On the other hand, based on results of analyses of actual semisubmersibles subjected to design waves, 12 kinds of foundamental load patterns were proposed to express loading conditions of connections by linear superposition of these foundamental load patterns. It was also confirmed that exial force applied to brace is dominant in structural strength of connection. Therefore, axial forces were mainly applied to braces in this study.Tests using several Kinds of small scale acrylic models and calculations by the FEM were carried out in order to discuss transmission mechanism of load between internal reinforcement members of connection. It was clearified by thid study that such a case where a brace penetrates column shell wall and it is supported by a hrizontal diaghragm is the most effective from stress flow and weight minimizaing view points.Buckling-collapse strength was studied by samll scale steel model tests and FEM calculations on specimens with differenct internal reinforcement members. It was concluded by these investi- gations that connections with brace penetration and internal supporting memberf of horizontal diaghragm or ring girder have relatively high resisntance to buckling-collapse. In the latter case, selection of face plate and appropriate allocation of tripping brackets for web platge of ring girder are important.By using both small and large scale steel models, fatigue tests were carried out. It was clarified that the reinforcement method mentioned above showe high resistance to fatigue. Moreover, significance of crack initiation life, through-thickness life and failure life was discussed as a general aspect of the case of specimens with complicated reinforcement members.