Rearch On K-type Castle Steel Joint

With the advantages of lightness, beauty and lower steel consumption, steel tubular structures have got a quick development and wide application in China. Castle steel joints which are being applied to the civil engineering by the designers represent many advantages such as beauty, freely design and safety. By the aid of element analysis software-ANSYS, comparison of K-type castle steel joints and tubular joints in respectes of ultimate strength and rotation stiffness is presented. Inelastic large stress finite element analysis of K-type castle steel joint under the change of various geometric parameters is developed too. The full loading-displacement path is traced, on which the ultimate strength of the joints were determined. Some factors including grid precision, boundary condition and material properties were also considered in the analysis. Considering the advantages of 10-node solid element and 4-node shell element, the writer applies them to castle steel joints and tubular joints respectly to make the computed ultimate strength results closer to the real solution. Analysis proves that, if designed reasonably, K-type castle steel joints only yield to axis force at the connection with the steel tubes. The fracture forms of crushing and excessive deformation due to the pulling and pressing of the branch tubes can be avoided, which can improve the safety of the structures. After the finite element analysis of K-type tubular joints and K-type castle steel joints, it is presented that the K-type castle steel joint can not be regarded as both hinged joint and rigid joint. Due to the rigid zone, the rotation of the tubes connecting to the castle steel joints is limited, and the calculating length of the tubes is reduced. A method of calculating the rigid zone dimension of the castle steel joint is presented, which is obtained by the combination of calculation and formula deduceing. Then various geometric parameters that determine the dimension of K-type castle steel joints' rigid zone are analyzed. And the paper presents the tendency of the rigid zone's dimension along with some geometric parameters. Finally, by means of numerical method, a formula can be used to calculate the demension of K-type castle steel joints' stiffness zone is brought out.At last, the paper brings forward some initial researches on the rationality of the joints' construction from the view point of the production technics of castle steel and give some coads and suggestions to engineering design, which will be benefit to the designers.