Experimental And Theoretical Research On The Out-of-plane Bending Rigidity Of Steel Circular Tubular Cross-joints

As the industry of steel boosts, steel tubular structure rises up. Recently, due to plenty of advantages, steel tubular structure is more and more widely applied in industrial and civil buildings. In steel tubular structures, the form of joints that connect components is crucial, whose behavior is related to the global structure directly. Connections between hollow section steel tubes are usually configured by welding one member directly to the surface of the other, which is called circular tubular joint. Loads always cause local deformation at the connection of chord and branch, which brings the relative deformation and rotation at the ends of the branches, the behavior of the joints is neither as same as the hinge nor the rigid connections whether in elastic or in elastic-plastic phrase, the semi-rigidity characteristic of the joints has obvious influence on the internal force, deformation and global stability of the tubular structures.Based on references from home and abroad, as well as the reviewing of the research achievements relating to this problem, in combination with a engineering background, the out-of-plane rigidity of circular tubular cross-joints is analyzed through the general finite element analysis software ABAQUS.At the first deformation mechanism of circular tubular cross-joint under out-of-plane bending load and definition of out-of-plane bending rigidity are represented briefly. Taken the Dongying airport as engineering background, two types of joints-unreinforced joint and reinforced joint with large size and full scale are designed, then tests and analysis on out-of-plane bending rigidity are carried out. Compare by the fact that test results and finite element analysis results verifies analytical applicability of finite element method.Then systematical researches are performed on identification and determination of parameters influencing out-of-plane non-rigid behavior of tubular joints. Non-linear finite element analysis is conducted on many tubular joint models with 8-nodal hexahedron element. Single-parameter analysis is conducted on three non-dimensional geometric parameters, which proves out-of-plane bending rigidity can be influenced by the ratio of brace's diameter to chord's diameter, the ratio of chord's radius to thickness and the ratio of brace's radius to thickness differently. Based on all the calculated results, a formula for the rigidity is fitted. as to the joints that have high diameters'ratio, relatively big axial compression forces could bring about great reduction on the rigidity.At last, several strengthening methods for tubular joints are analyzed by finite element method. In combination with the previous results, a reasonable scheme is picked, and can be referred to by engineering projects.