Study On The Effect Of Welding Residual Stress On The Flexural Mechanical Properties Of Hollow Spherical Joints

The welded hollow spherical joint(WHSJ)is one of the common forms of connection large-span spatial grid structure members.It is simple in composition and easy to construct.However,the thermal effect inevitably leads to welding residual stress in the welding process;and elimination of welding residual stress is not usually performed on the ball-tube butt weld of the WHSJ during the actual construction of the structures.Existing studies have shown that welding residual stress will weaken the mechanical properties of the member,such as reducing the axial stiffness of the WHSJ.Therefore,the study of welding residual stress on the WHSJ’s mechanical property is necessary.The WHSJ is a semi-rigid joint,which can transfer not only axial force but also a certain amount of bending moment.But few studies have considered the effect of welding residual stress on the WHSJ’s flexural performance.Thus,the study for the effect of welding residual stress on the WHSJ’s mechanical property as ultimate flexural capacity,flexural rigidity is both the prerequisites for the research on foundation components and the basis of research on the overall structure.For this reason,this paper uses a combined numerical simulation and test research approach to study the WHSJ’s ball-tube butt weld.The simplified distribution of weld residual stresses in the WHSJ section is studied as well as the change in the WHSJ’s ultimate flexural capacity,flexural rigidity when considering welding residual stresses.Further,the effect of welding residual stress on load-bearing capacity and deformation of the single-layer reticulated dome is briefly analyzed.The main research contents and results are as follows:(1)The welding process of the WHSJ’s ball-tube butt weld was simulated through ANSYS.Simplified welding residual stress distribution patterns based on the von mises stress criterion for the WHSJ sections are obtained.The influence trend of every parameter on the WHSJ’s welding residual stress distribution is analyzed based on joints’ dimensions.The research shows that the WHSJ’s welding residual stresses up to 220MPa;The WHSJ has a certain heat affected zone whose extent is mainly influenced by the dimensional parameters.(2)The control specimens on the WHSJ with and without weld residual stresses are prepared.The pure bending tests of the WHSJ are carried out.The moment-rotation curves of the specimens are obtained and the parameter values such as flexural elastic limit,bending yield load,ultimate flexural capacity and flexural rigidity are obtained by the drawing method.The test results show that the welding residual stress on the joint ultimate flexural capacity does not exceed 5%,while the maximum flexural rigidity can be weakened by 10.43%.(3)The effect of welding residual stress on the WHSJ’s flexural mechanical properties is parametrically analyzed based on the WHSJ’s construction dimension parameters.The correspondence between the effect of welding residual stress on the WHSJ’s mechanical property and the construction dimension parameters is determined qualitatively.When the WHSJ’s flexural rigidity is larger,the effect of welding residual stress on it is weakened,and vice versa is strengthened.(4)Through the bilinear spring model,the ultimate bearing capacity and deformability of K8 type single-layer reticulated dome are finely simulated and analyzed.The results point out that when the effect of weld residual stress on the joint is considered in the most conservative case,the overall structural ultimate bearing capacity decreases by 7.19%,and the maximum deformation increases by 11.93%.