【作者】 唐海军；

【导师】 董石麟；

【作者基本信息】 浙江大学 ， 结构工程， 2005， 硕士

【摘要】 焊接空心球节点是我国采用最早也是目前应用较广的一种节点，具有构造简单，传力明确，连接方便等优点。对于这种节点的极限承载力，国内外做了大量的试验与理论研究，并提出了一些承载力的经验和理论计算公式，但总的来说，对于空心焊接球节点的认识还是不够深入和全面的。特别随着实际工程运用的不断发展，这种局限性也逐渐显露出来，比如，在国家游泳中心“水立方”多面体空间刚架结构中，焊接球节点除承受轴力、还承受相当大的弯矩，而目前规范对焊接空心球节点在轴力和弯矩共同作用下的承载力设计方法尚属空白。因此，本文在总结前人工作的基础上，分别对焊接空心球节点在轴力作用下、弯矩作用下以及轴力和弯矩共同作用下的承载力进行了理论和试验的研究。 本文采用理想弹塑性应力—应变关系和Von—Mises屈服准则、同时考虑几何非线性的影响，建立了焊接空心球节点的有限元分析模型，对承受轴力、弯矩及两者共同作用的空心球节点进行了大量的非线性有限元分析。通过对这些节点的应力、变形分析研究，了解了空心球节点在不同荷载组合作用下的受力性能和破坏机理；通过弧长法迭代跟踪球节点的位移——荷载曲线，从而得到不同型号空心球节点在不同荷载组合下的极限荷载力。 本文通过简化焊接空心球的边界条件，利用弹性薄壳有矩理论给出了轴力作用下空心球节点的内力、变位和应力的分布规律，从而求得最大应力点的Mises等效应力，由强度条件得出焊接空心球节点在弹性阶段的最大承载力。并通过算例分析，验证了这些薄壳理论解与有限元结果的一致性。 在总结前人工作及本文有限元研究成果的基础上，依据焊接空心球节点极限破坏为冲剪破坏、冲切环面上剪应力起控制作用等特征，本文又提出了在轴力、弯矩及两者共同作用下焊接空心球节点承载力的简化理论解。 为验证了有限元模型的正确性，同时为节点极限承载力提供最直接的验证，本文选取若干典型节点进行了试验研究。 在综合以上简化理论解、有限元分析和试验研究的结果的基础，本文提出了轴力和弯矩共同作用下的节点承载力实用计算方法，可供实际工程设计采用，也可供相关规程修订时参考。 最后，针对工程中焊接空心球节点处于空间多向作用的实际情况，本文选取了最简单的四管正交、双向作用下的焊接空心球节点进行了有限元法分析，得出双向作用下焊接空心球节点承载力的一些规律，并提出修正系数表达式，对实用计算方法作了一些修正。更多还原

【Abstract】 Welded hollow spherical joints are the earliest used kind of joints in our country, and are widely used for their simple structure, definiteness of load transferring and convenient connection. A great deal of experimental and theoretical studies have been made for the ultimate load-carrying capacity of the joints by many domestic and foreign researchers, and many empirical and theoretical criteria for the load-carrying capacity were proposed. However, the knowledge about the welded hollow spherical joints is generally shallow and non-overall. With the development of the utilization of the practical engineering, such limitations are gradually coming out. For instance, the welded hollow spherical joints in the polyhedron space frame structure for National Swimming Center "Water Cube" are subject to both axial forces and large bending moments. However, no provision has been provided by current design codes for welded hollow spherical joints subject to combined loading. So based on the summarization of the former work, theoretical and experimental researches are made on the ultimate load-carrying capacity of the welded hollow spherical joints subject to axial forces, bending moments and combined loading of the two kinds.Based on the elastic-perfectly plastic model and the Von-Mises yielding criterion, a finite element model for the analysis of welded hollow spherical joints is established, in which the effect of geometric nonlinearity is also taken into account. Employing the nonlinear finite element model, a great deal of parametric studies are carried out on the welded hollow spherical joints subject to axial forces, bending moments and combined loading of the two kinds. By the researches on the stresses and deformation of the joints, structural behavior and the collapse mechanism are investigated for the welded hollow spherical joints subject to various combinatorial loading. The arc-length iterative method is used to follow the loading-deformation curve of the node, and the ultimate load-carrying capacity for different types of joints subject to various combinatorial loading is obtained.Combined the simplified boundary conditions of the joints and the moment theory of elastic shell, the distributions of the internal force, displacement and the stress of the joints under axial force are derived. An example is given to validate the conformity between the theoretical and the finite element results. The maximum load-carrying capacity of the joints in the elastic stage is also obtained according to the Von-Mises yielding criterion.By the summarization of the former work and the finite element analyses in the thesis, and based on the punching shear failure model and the shear stress controlled condition, a simplified theoretical solution is also proposed in this thesis for the loading-carrying capacity of the joint under the combination of axial force and bending moment.Experiments on five typical full-scale joints are conducted to provide directly the evidence of the ultimate load-carrying capacity for the joint, and also to validate the finite element model.Finally, by summarizing the results from the simplified theoretical solution, finite element analyses and experimental study, a practical calculation method is proposed for the load-carrying capacity of the joints subject to combined loading. The results from this study can be applied for direct design use, and also provide a reference for the revision of relevant design codes.At last, as the welded hollow spherical joints in practical engineering are usually multi-directional in the space, finite element analyses are carried out for the simplest four-tube orthogonal and bidirectional joints in the thesis. Some rules are obtained for the load-carrying capacity of the bidirectional joints. The practical calculation method is modified and the expression of the modified coefficient is also proposed.更多还原