The Influence Of Welding Residual Stress On Ultimate Bearing Capacity Of Multiplanar KX-type CHS Joints

KX-type CHS joints had been widely used in large-span space structures. In theprocess of welding, the larger welding residual stress was generated because of someweldings in the joints. Welding residual stress in some cases could even reach thematerial yield limit, resulting in decline of the bearing capacity in the joints anddecrease of the structural safety properties. There were no clear specifications tomultiplanar KX-type CHS joint in code for design of steel structure. And, the weldingresidual stress was not considered in the past study of KX-joint. Therefore, in order tobetter understand the mechanical properties of KX-joint, the influence of weldingresidual stress on ultimate bearing capacity of multiplanar KX-type CHS joints werestudied in this paper.In this paper, ANSYS software was used to simulate and analyze the weldingprocess of KX-joint. And, there were three questions to be studied, including thewelding temperature field、the welding stress field and influence of welding residualstress on ultimate bearing capacity of joints. Weld metal filling process was simulatedsuccessfully by the birth and death elements technology of ANSYS software and we gotthe distribution law of welding temperature field. After that, the distribution of weldingstress field was obtained by defining boundary constraints and applying temperatureload on the finite element model. In the end, the ultimate bearing capacity was got byapplying load to KX-joint with considering the residual stress and without consideringthe residual stress. The influence of welding residual stress on ultimate bearing capacityof KX-joint was studied by comparing with the ultimate bearing capacity withconsidering the residual stress and without considering the residual stress.In this article, twenty-six KX-joint models were chosen and studied. The researchcontents were as follows.①In order to calculate the welding temperature field and analyze the distributionlaw of temperature field, this paper defined the element types and material properties ofKX-joint, established the finite element model, meshed by a combination of free andmap mesh, applied the welding heat source by the birth and death element technologyand chose suitable load steps and time steps.②In order to calculate the welding stress field and analyze the distribution law ofstress field, this paper defined boundary constraints on the finite element model and toke the node temperature in the thermal analysis as the load applied to the model.③This paper calculated equivalent residual stress of KX-joint and obtained thedistribution law of welding residual stress when parameters γ (the ratio of diameter tothickness)、β (the diameter ratio of head tube to branch tube)、θ (the axis angle of headand branch tube) changed.④This paper calculated ultimate bearing capacity of K tube with considering theresidual stress and without considering the residual stress when X tube was pressed orpulled. In the meantime, welding residual stress on ultimate bearing capacity of K tubeas the change of parameters γ、β、θ was studied.⑤This paper calculated ultimate bearing capacity of X tube with considering theresidual stress and without considering the residual stress. Welding residual stress onultimate bearing capacity of X tube as the change of parameters γ、β、θ was studied.