Finite Element Analysis On Tensile Strength Of Hollow Spherical Joints Base On Generalized Strength Model

Large-span spatial structures are currently the fastest growing form of the structure.Large-span building,and as the spatial structure of its core technology developments are one of the important symbols of a country's level on building of science and technology.Hollow spherical joints structures are now the most widely used form of nodes.Although now the research on hollow spherical joints has mainly focused on the status of one-way force.However,the actual hollow spherical joints are in a state of multinomial stress,while the tensile strength of the hollow spherical joints which in the state of planar bis(many) and space force,there is currently no systemic and in-depth analysis.When hollow spherical joints is in state of pulling,there is serious tensile stress concentration on pontes between circular steel bar and ball node.There are more serious of the tensile stress,more easily to occur ductile-brittle fracture,so this region is more likely to have first crack then result in loss of carrying capacity of hollow spherical joints.Ductile-brittle fracture of steel structures are a special problem,the traditional strength calculation can not solve this problem.China's steel structure design specification of the building have no specific formula on steel fracture control design,it only just give the structural recommendations on how to prevent brittle fracture of steel in cold regions.Based on ANSYS Parametric Design Language(APDL) and User Programmable Features(UPFs),secondary development of ANSYS was implemented with the subroutine of generalized hydrostatic yield model,and implantation of ANSYS material model library.Tis paper simulated tensile strenghth on the case of 120 welding hollow ball nodes in single axial tension and as well as 108 nodes in three axial tension.Based on the situation in single axial tension,we examined the stress distribution in the connecting region of welding hollow ball,at same time,made use of the ellipsoid metal fracture criterion,to forecast the initial crack location of the hollow ball and give a prediction of its design capacity formula.Based on the situation in three axial tension,we usd a similar method of analysis to examine the location of the initial fracture,and give a formula on the three axial tension situation. In this paper,the results will provide a reference on damage mechanism and design on further research of welding hollow in many axial tension situation.