轴力和弯矩共同作用下焊接空心球节点承载力研究与实用计算方法

LOAD-CARRYING CAPACITY AND PRACTICAL CALCULATION METHOD FOR WELDED HOLLOW SPHERICAL JOINTS SUBJECT TO COMBINED AXIAL FORCE AND BENDING MOMENT

国家游泳中心“水立方”多面体空间刚架结构中 ,杆件除承受轴力外 ,还承受相当大的弯矩 ,但目前规范对焊接空心球节点在轴力和弯矩共同作用下的设计方法尚属空白。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。通过典型节点的试验研究 ,直观了解节点的受力性能和破坏机理 ,并验证了有限元模型的正确性。文中还推导了基于冲切面剪应力破坏模型的节点承载力的简化理论解。最后 ,综合简化理论解、有限元分析和试验研究的结果 ,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 。

Members in the polyhedron space frame structure for the 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. Based on the elastic-perfectly plastic model and the Von-Mises yield 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 major parametric study is carried out on the joints subject to axial forces, bending moments and combined loading of the two. Experiments on five typical full-scale joints are conducted to understand directly the structural behavior and the collapse mechanism of the joint, and also to validate the finite element model. A simplified theoretical solution is also derived for the loading-carrying capacity of the joint, based on the punching shear failure 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.