Bearing Capacity Research Of Circular Hollow Section(CHS) Brace-H Section Chord KT-joints

The unstiffened joints have the characteristics of high bearing capacity,convenient construction and so on.They are widely used in large span structures such as airports,railway stations and factories.Scholars at home and abroad have done a lot of research on the tubular joint,but few of them have been involved in the formation which is made of steel pipe braces and steel chord.In this paper,KT type CHS braces-H section chord joints is taken as the object of study.The mechanical properties were studied by experiment and analysis.Two lapped KT type CHS braces-H section chord joints is made according to the actual engineering.One is equipped horizontal stiffening plates and the other one not.A reaction frame is designed on the base of the direction of the member bars of the joints.The loading test is done by the jacks and the ultimate bearing capacity and failure modes of the two joints are obtained.The finite element model of the specimen is established by using the shell element in ANSYS finite element software and considering the material nonlinearity and geometric nonlinearity,bearing capacity of the joint is studied.The finite element results are compared with the experimental results.The comparison between the two results shows that the finite element modeling method is correct and reasonable.In addition,the paper also proposes several strengthening and improving methods of KT type joints.One is to set the pad on the edge of the chord to strengthen the plate.The load influence the plate first and then distribute to the plate and improve the stress concentration of the upper flange of the chord.Second is set a gusset plate among the braces.The gusset plate to coordinate the load of branch and Improve the overall bearing capacity of the joints.Finally,this paper also puts forward some improvement measures for the joint which has the lateral transverse stiffening plate.This mean changing the stiffening plate position so that it is close to the axis of the web,increases the stiffness of the joint.The above methods are analyzed by finite element software,which proves that the improvement measures increase the stiffness of the nodes and improve the bearing capacity of the joints.The results of this paper show that the failure mode of the joint is related to its bearing mechanism.In general,the axial stiffness of the chord is much greater than the radial stiffness.The chord is mainly bent by the upper flange to bear the load of the web.The bending deformation of the upper flange of the chord is too large.The failure mode is the chord plastic damage.The chord is reinforced in the radial direction,and the chord is primarily responsible for the load of the braces through the shearing force of the chord.The bearing capacity of the joint is controlled by the brace which is under the pulling force.