The Theoretical Study Of Cast Steel Branch Joints In Tree Structures

With the increase of requirements for beautiful architectural appearances and the rational forceperformances in spatial structures, a kind of tree-like structure based on the principle of bionicsconstruction shows a broad application prospect. Joints are the key areas in the tree-like structure. Since thecast steel joints can avoid the stress concentration caused by seam welding, so they have been used widelyin the tree-like structures. But the basic theoretical studies of cast steel branch joints are still relativelyscarce currently and the existing codes have no articles for reference. In projects, we have to apply thegeneral finite element program combining with experimental verification to design the specific joints used.The study of the modeling method, mechanical properties, theory of computation and structuraloptimization of cast steel branch joints is few. This paper described the application prospect of tree-likestructures, overviewed the research status of cast steel joints and completed the following research works:(1)This paper succeeded to setup the modeling of cast steel branch joints with smooth transitionshape using three dimensional modeling software SolidWorks.(2)This paper accomplished the nonlinear finite element analysis of the cast steel joints with twoforks and three forks under axial loading and grasped their characteristics of stress distribution and failuremodes: The cast steel joints with two forks and three forks with different parameters yield firstly on thecore area of the joints, and then the plastic regions expand until the damage. The destroy of the joints aremainly caused by the plastic hinge formed on the core area.(3)This paper proposed the forms of the formula of the cast steel branch joints throughreferencing the formula of ultimate bearing capacity of welded joints and the results of the regressionanalysis. Then conducted the regression analysis using the results of finite element analysis to determinethe pending parameters of the formula. Finally transfer the formula of ultimate bearing capacity to theformula of design calculation bearing capacity in order to set a safety factor K according to therequirements of <Technical specification for application of connections of structural steelcasting>(CECS235:2008). The formula of design calculation bearing capacity of the cast steel joints withtwo forks and three forks are respectively equation1and equation2: This paper described the modeling method of the cast steel branch joints with smooth transition shape and conducted the nonlinear finite element analysis of the cast steel joints with two forks and three forks under axial loading considering the nonlinearity of materials and geometry. Then this paper obtained the formula of design calculation bearing capacity under axial loading through regression analysis by ORIGIN7.5. Moreover, this paper applied the bearing capacity to the design formulas, providing references for related engineering design. Because the cast steel joints with two forks and four forks have a large degree of similarity, so this paper did not study the cast steel joints with four forks.