Rotational Stiffness Research Of Q690Tubular Joint Used In Herringbone Column And Cross-brace

Joints stiffness is extremely important in the design of the steel tower structure.When the stiffness of joint can not achieve the requirements of the jonts stiffness of theoverall structure, measures will have to be taken to strengthen the joint. The previousformula can not be reused, the domestic and international norms rarely involve designformula of the jonits strengthened. The research has theoretical significance. In addition,high-strength steel, due to the high intensity, in the same design load can reduce themember section, thus saving material, producing high economic efficiency. And it hasbeen widely used in bridges, power tower and span space structure. Therefore, thereaserch of the mechanical properties on the Q690enhanced tubulr joints has animportant practical significance. In this paper, based both on test and numerical analysismethord, the author research the rotational stiffness of Q690tubular joint used inherringbone column and cross-brace.(1) Select1:1model of herringbone column and stull tubular joints of steelframework designed by a design institute, and design4sets8specimens, in whichcomprise2unstrengthen specimens,2specimens enhanced by tile form board,2specimens enhanced by inner annular plate, and2specimens enhanced by inner sleeve.The European Specification about rotational stiffness definition of the joints and rigidjoints, semi-rigid joints, hinged joints is referenced as the verdict criteria. The impact ofthe performance of joint rotational stiffness in different ways of strengthening is studiedpreliminarily, and the difference of the different ways of strengthening between therotational stiffness was compared and analysed. (2) Using ANSYS finite element software, and the constitutive relation from thematerial test, based on the experimental data, the accuracy of the finite element model isverified. The influence of the stiffness of the joint in different ways of loading andlength of the chord member is analysed. And in order to studying the influence of thevariable parameter on the stiffness of the joint, the variable parameters are analysed.Inorder to selecting the appropriate approach of extracting initial stiffness, the differentmethods of calculation of innitial stifness is compared and analysed Finally, based onthe standard model, the influence of ratio of axial compression stress to strength on thestiffness each joint model is studied.(3) The results show that Although strengthening plate/ring of columns can greatlyimprove the rotation stiffness of the junction made by herringbone column and stulltubular joints, according to the criteria in European norms, enhanced joint is still asemi-rigid joint. The thickness of the strengthen plate, has affected the initial stiffness ofthe joints enhanced by tile form board and by inner annular plate For the ductility of thejoints enhanced by tile form board is better than the joints enhanced by tile form board,thus the joints enhanced by tile form board is chosen The spacer and width of innerannular plate both can affect the initial stiffness of the joints, however, the width of theinner annular plate is more significant to the initial stiffness. Compared with the othertwo ways, because of the remarkable ductility and stiffness the type of inner annularplate is recommended as the first choice.