Effects Of Internal Ring-Stiffeners On The Behavior Of Steel Tubular Joints

In recent years, hollow section structure has been widely used at home and abroad. In hollow section structure, joint is one of crucial components. Its damage often leads to failure of members which connect with it, even the whole structure. At present, simple joints are widely used in hollow section structures and can not satisfy the strength requirement in some cases. To improve the bearing capacity and fatigue life of simple joints, commonly we use different methods as enhancing measure, and mostly the solution we choose is setting ring-stiffener in main tube. The distribution of stress in stiffened joint is very complex. It is important to control the stress and strain of joints in designing and manufacture, therefore the research of ring-stiffened joint has important theoretic value and broad application prospect in the development of hollow section structures.Ring-stiffened joints (including X-joints and multiplanar stiffened joints) were investigated in this thesis, work mainly included:Based on references of domestic and abroad, the research achievements of hollow section structures and relevant knowledge of simple joints were introduced. At the same time, the development history of internally ring-stiffened joints was reviewed, the research status and present problems were expounded, and the main research contents of this thesis were put forward.Based on the theoretical analysis methods about internally ring-stiffened joint of domestic and overseas scholars, the theoretical analysis method used in this study was introduced, and finite element method and related contents of ANSYS were summarized briefly.A finite element model of ring-stiffened X joint was established with ANSYS, and four X joints which had different settings of stiffener was tested and analysed with nonlinear finite element method. And then, theoretical results were compared with test results respectively, including strain, displacement, the ultimate load capacity and failure mode. In this way, the finite element modal was validated. After that, the effect of the parameters of ring-stiffener (including ring-stiffener thickness, width, spacing and so on) to ultimate load capacity of stiffened X joint was analysed, and the formula of ultimate load capacity reinforcing multiples of ring-stiffened X joint was proposed using regression techniques.Based on Dalian international conference center project, the multiplanar joint which bears heavy loads and has poor strength without ring-stiffener was analysed using ANSYS non-linear finite element analysis method. The setting of each key parameter in finite element model was briefly introduced, and the effects of ring-stiffened spacing on strength, stiffness and failure modes of stiffened joints were systematically analyzed while keeping other parameters constant. Then, some reasonable detailed requirements of internal stiffeners were given, which provided some theoretical basis for designing of this project.In the end, the main achievement of this study was summarized. At the same time, some directions for future research in ring-stiffened joints were suggested.