Research On Stiffener’s Height Control Method In Concrete-Filled Steel Tubular Column-Steel Beam Flange Connection Joint

The concrete-filled steel tubular column-steel beam exterior stiffener ring connection joint is a commonly used beam-column connection scheme for high-rise building structures.This joint is a key part of transfering internal forces and bearing loads,and has good bearing capacity and seismic performance.Flange connection of concretefilled steel tubular column-steel beam outer reinforcement ring connection is a newly proposed joint connection method.It uses flange plates and bolts to connect concretefilled steel tubular columns.Its characteristic is that rigid flanges and reinforced ring plates are assembled on the beam and column.The node area has the characteristics of high assembly rate and convenient construction.The joint connection method is not perfect at present.The core problem is that the stiffener height of some rigid flanges is relatively large,and the stiffener protrudes from the floor slab,which affects the use of the building,and its design method is relatively conservative,resulting in the large amount of steel used for flanges and stiffeners.Therefore,in-depth study of the force characteristics of the new type of joint rigid flange,optimization of its design method,and proposed control measures for the height of stiffeners have important engineering practical significance and value.In this paper,the yield line theory is used to analyze the force characteristics and calculation methods of the traditional stiffeners of rigid flanges and the new type of upper ring stiffeners,and the general finite element analysis software Abaqus is used to analyze the force laws of the two stiffeners.The parameter analysis is carried out,and the height control measures and design methods of the stiffeners of the flange-connected concrete-filled steel tubular column-steel beam outer reinforcement ring joint are proposed.Finally,the proposed height control method is verified by the finite element calculation example and results of Shaking table test.The main research contents and conclusions of this paper are as follows:(1)Take the academician building project of the Shenzhen Changzhen demonstration project and the Chengdu Xinxing Industrial Park Service Center Building 1-1 of the Sichuan Province Promotion Prefabricated Construction Demonstration Project as examples,the traditional stiffener calculation method is used to design the stiffeners of the flange-connected concrete-filled steel tubular column-steel beam outer reinforcement ring joint,and there is a phenomenon that the stiffening ribs protrude from the floor,and further optimization is needed.(2)Improved the traditional stiffener design method of flange connection nodes.By changing the number of bolts,the distance from the outer wall of the steel pipe to the bolt center,the thickness of the stiffener,the form of the T-weld between the stiffener and the steel pipe,and the optimization of the ratio coefficient of the force transmission of the stiffener,the position of the rotation axis of the flange section,etc.Traditional stiffener height control measures are proposed.The shortest force transmission path model based on the elastic method and the flange yield line model based on the elastoplastic method for calculating the stiffener transmission ratio are established respectively,and the calculation results are compared with the value of the specification.The finite element calculation example shows The calculation results based on the flange yield line model are more consistent with the actual values.The position of the rotation axis of the flange section of the flange-connected concrete-filled steel tubular column-steel beam outer reinforcement ring node during the seismic check phase is optimized.The finite element calculation example shows that the rotation axis is located near the outer wall of the column steel tube during the seismic check phase.(3)Established a new design method of stiffener with upper ring.The upper ring stiffener is divided into several T-shaped sections for analysis,and the force characteristics of the T-shaped section steel beam are compared,and the contribution of the upper ring to the shear resistance of the vertical stiffener is studied.Refer to the outer strengthened ring plate,this paper analyzes the effective width of the steel pipe participating in the tension of the upper ring and uses the yield line theory to derive the calculation formula for determining the width of the upper ring.This paper analyzes the effect of height control measures on the amount of steel used is discussed and the feasibility of part of the ring stiffeners is discussed.(4)Using the stiffening rib height control measures proposed in this paper,taking two actual projects as examples,the structural design of the flange-connected concretefilled steel tubular column-steel beam outer reinforcement ring joint was carried out,and the finite element analysis of the beam-column composite specimen was carried out to verify The effectiveness of the stiffener height control measures proposed in this article.(5)The design of the beam-column connection nodes of the 1/3-scale shaking table model of the primary and secondary hybrid frame structure with flange-connected concrete-filled steel tube columns-steel beam outer reinforcement ring connections is carried out on the main frame.The strong seismic response of two traditional stiffener nodes and four new stiffener nodes with upper ring are discussed.The effectiveness of the stiffener height control measures proposed in this paper has verified.