Experimental Study On Static Behavior Of Assembled Joints Of Steel Staggered Truss To Concrete-Filled Square Steel Tube Column With Sleeve-Type And End-Plate Connections

Because of its flexible and excellent economic performance,the staggered truss structure has been widely used and studied abroad.Since the beginning of this century,our country has carried on a series of research on this kind of structural system.At home and abroad,some studies have focused on the overall performance of the structure,and the research on the connections of truss columns and trusses is less.In this paper,a sleeve-type and end-plate joint is proposed with reference to the existing joint form.In order to study the performance of this kind of joints,three1:2 scale specimens of up-chord joints and three bottom-chord joints are designed and simulated.The results show that the axial compression ratio,the concrete strength,the extension length of the connecting beam and the section size of the connecting beam on the performance of the up-chord joints are analyzed by ABAQUS nonlinear finite element calculation program.The influence of the extended length of the sleeve,the wall thickness of the sleeve and the width of the flange on the bearing capacity of the bottom-chord joints is studied.The ultimate bearing capacity of the bottom-chord joints under the action of the tension is deduced by the plastic hinge theory and compared with the finite element calculation and the experimental results.This paper draw following main conclusions:(1)The bearing capacity of the up-chord joints is greatly influenced by the connecting short beam.When the short beam is weak,it can be regarded as energy dissipation beam,and when the short beam is strong,the steel tube below the sleeve is broken.The bearing capacity of the joints increases with the increase of the strength of the concrete.When the axial compression ratio and the length of the connecting short beam increases,the bearing capacity decreases and the short beam size of flange has a slight effect on the bearing capacity of the joints;(2)When the sleeve extension length is within a certain range,the bottom-chord joints have the highest bearing capacity under the monotonous tension.The bearing capacity of the joints is proportional to the square of the thickness of the sleeve.The larger the width of the flange of the connecting short beam is,the higher the bearing capacity is;(3)The formula of the ultimate bearing capacity of the bottom-chord joints based on the theory of plastic hinge is in good agreement with the experimental results and the finite element calculation results.The formula of this paper can provide reference for engineering design.