Study On The Mechanical Performance Of Complex Steel Tubular Spatial Joint

Under the background of one belt and one road and the rapid development of new infrastructure,the application of steel tubular tower in UHV transmission lines is increasingly widespread.The steel tubular joint is the most important part of the steel tubular tower.For the common simple steel tube joint,scholars both domestic and overseas have done a lot of research,but for the complex steel tubular spatial joint research needs to be further improved.In this paper,based on the finite element analysis,the mechanical properties and bearing capacity of the complex steel tubular spatial joints are studied.（1）The finite element model of the complex steel tubular spatial joint considering the material nonlinearity and geometric nonlinearity is established by the finite element software ABAQUS.The shell element is used to simulate the steel tube,and the beam element is used to simulate the bolt.Compared with the test data,the failure mode of the joint model is the same as that of the test,which is the concave deformation of the chord wall;the load displacement curve trend of test and model are consistent with each other;the difference between the ultimate bearing capacity is small,the ratio of model to test is 1.04;the finite element model is verified.（2）The complex steel tubular joint is parameterized based on the confirmed finite elementmodel,and it’s bearing capacity is studied by the influence of the angle between brace and chord（θ₂）,theradius-thickness ratio of chord（γ）,the ratio of diameter between brace and chord（β₂）,the ratio of wall thickness between brace and chord（τ₂）.The results show that there arethree failure types:the first one is the curvature of chord,the second is thebending of compressed brace,the third is the local-buckling of brace.The bearing capacity of the complex steel tubular joint is enhanced by increasingβ₂andτ₂,and reducedby increasingθ₂ andγ.Then based those data above,a simplified formula for the ultimate bearing capacityof the joint is fitted by using the method of multiple linear regression,and the ratio of the ultimate bearing capacity of the simplified formula and the FEA results is between 0.93 and 1.13,the fitting formula value is in good agreement with the finite element value.（3）In this paper,the bearing capacity of complex steel tubular spatial joints with positive and negative eccentricity of brace is studied,and the corresponding finite element model is established.The bearing capacity of joints with eccentricity of brace in the range of-0.25D≤e≤0.25D is calculated.According to the calculation results,when the eccentricity range is 0～0.25D,the joint bearing capacity increases under the condition of negative eccentricity of brace,and decreases under the condition of positive eccentricity of brace;when the negative eccentricity is e=-0.25D,the ultimate bearing capacity of the joint increases by 30.8%,and when the positive eccentricity is e=0.25D,the ultimate bearing capacity of the joint decreases by 6.8%.Three different levels of axial force are applied to the chord,and the influence of the chord axial force on the bearing capacity of the joint under the condition of eccentricity of brace is analyzed.