LOAD-CARRYING CAPACITY AND PRACTICAL DESIGN METHOD OF WELDED HOLLOW SPHERICAL JOINTS IN SPACE LATTICED STRUCTURES

摘要

A newly developed space structure, the polyhedron space frame based on the bubble theory, is adopted in Chinese National Swimming Center-the Water Cube for 2008 Beijing 29th Olympic Games. Circular hollow sections, square hollow sections and rectangular hollow sections are employed as structural members, while welded hollow spherical joints are employed to connect the members. However, for welded hollow spherical joints connected with rectangular/square steel tubes, no previous study has been reported and no design criterion has been established. This paper investigates the structural behavior and load-carrying capacity of the joints subject to axial forces, bending moments and combined loading of the two. Based on the elastic-perfectly plastic model and the Von-Mises yield criterion, a finite element model for the analysis of the joints is established, in which the effect of geometric nonlinearity is taken into account. A major parametric study is then carried out employing this model. Experiments on ten 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, and the basic form for the design equation is obtained. Finally, by utilizing the results from the simplified theoretical solution, finite element analysis and experimental study, the practical design method is established for the load-carrying capacity of the joints subject to axial forces, bending moments and the 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