Research On Mechanical Behavior And Design Method Of KK Type Steel Tubular Joints

The complexity of steel structures determines the diversity of joint forms.The design formula of joints in the specification is put forward under certain assumptions,that is,the steel pipe only bear the effect of axial force.Obviously,this assumption does not accord with the actual engineering stress.Especially the large span and large-size intersecting joints are subjected to the combined action of axial force and bending moment.At present,the research of small size intersecting joints under axial force is more mature than that of large size intersecting joints under composite force,so it is particularly important to carry out the related research.On the basis of the Specification for Design of Steel structures,this paper uses the finite element software ANSYS.by changing the influence parameters of the bearing capacity of the joints,a spatial KK type circular steel pipe intersecting joint model with different dimensions is established.The single parameter analysis method is used to study the mechanical behavior of KK circular steel pipe joints under axial force,bending moment and composite force,respectively.The orthogonal test method and multivariate regression technique are used to analyze and process the data of the nodes under various forces.The conclusions are as follows:1)under the action of axial force,the failure mode of different sizes of KK circular steel pipe intersected joints;the axial ultimate bearing capacity increases with the decrease of the diameter of the tube and the ratio of wall thickness(20???50),and increases with the increase of the ratio of branch to tube diameter(0.3???0.6).When(300°??? 50°)The ultimate bearing capacity of the joint decreases with the increase of the angle between the branch and the supervisor.When(500°?0 ?60°),the ultimate bearing capacity of the joint increases with the increase of the value,and with the change of the transverse angle between the branches and pipes(900°???120°),there is no obvious change.2)under the action of bending moment,the failure mode of KK circular steel pipe intersecting joints with different sizes;The ultimate flexural capacity increases with the decrease of diameter and wall thickness ratio(20??? 50),increases with the diameter ratio of branch pipe to supervisor(0.3??? 0.6),decreases with the increase of angle between branch pipe and supervisor(300°??? 60°),and decreases with the increase of branch pipe diameter ratio(900°??? 120°),there was no obvious change in the transverse angle.The relationship curve between the parameters and the bending bearing capacity of the KK type circular steel pipe intersecting joint is obtained,and the formula for calculating the bending bearing capacity of the KK type circular steel pipe intersecting joint is fitted.The formula meets the requirements of accuracy under the condition(20???50?0.3???0.6?30°???60°?90 ? ? ?120°)of satisfying the requirements of accuracy.3)under the condition of composite force,the calculation formula of bearing capacity of KK type circular steel pipe joint under axial force in code is verified,and the result of joint design based on this formula is not safe in actual engineering.At the same time,the paper explains the necessity of considering the bending moment of the joints,and gives the design basis of the KK circular steel pipe intersecting joints under the condition(20???50?0.3???0.6?30°???60°?90°? ??120°)of satisfying the requirements,which provides a reference for the design of practical engineering joints.