Research On Effective Distribution Width Of Tension X-Joints Of Rectangular Concrete-filled Steel Tube Stiffened With PBL

The rectangular concrete-filled steel tube joint stiffened with PBL is a new form of truss joint.At present,there are few studies on the mechanical performance of the new joint,which hinders the application and popularization of the concrete-filled steel rectangular tubular truss structure.The effective distribution width is an important parameter for studying the mechanical performance of the joints.To determine the stress mechanism of the rectangular concrete-filled steel tube joint stiffened with PBL,this paper uses ABAQUS finite element method,parameter analysis,and least-squares regression analysis to study the change rule of stress distribution and effectiveness with the joint construction parameters.The influence of the joint construction parameters on the tensile stiffness and bearing capacity is analyzed.The main research contents and results of this paper are as follows:（1）Simplified mechanical models of joints of rectangular hollow tube,concrete-filled rectangular steel tube and PBL stiffened concrete-filled rectangular steel tube are set up.The theoretical calculation formula of the tensile stiffness of the joints is proposed.The distribution of joint stiffness,the force mechanism and failure modes of the PBL stiffening ribs are analyzed.The influence of the structural parameters of the joints on the mechanical properties is deduced theoretically.（2）ABAQUS software is used to establish joint models,and the reliability of the finite element simulation method was verified by the exciting paper.On this basis,variable parameter analysis was used to investigate the stress distribution process of the joints and the stress distribution of the ultimate state.The influence rule of the internal fill concrete,PBL stiffeners,width to thickness ratio 2γof chord,the influence of the width ratioβof brace to chord,and the thickness ratioτof brace to chord to the effective distribution width of the joint and the ultimate bearing capacity were studied.According to the results of finite element calculation,the expressions of effective distribution width of rectangular hollow tube,concrete-filled steel tube and PBL stiffened concrete-filled steel tubular joints were obtained and the correctness of the formula is verified.（3）ABAQUS software is used to establish 112 finite element models of PBL stiffened concrete-filled steel tube joints.The influence of PBL stiffening ribs thickness t_PBL,distance between PBL stiffening ribs d_p,hole diameter D,the distance between hole d_h,and concrete mortise shear area S to the effective distribution width and the ultimate bearing capacity of the joint are studied by variable parameter analysis.Based on the results of finite element calculations,a calculation formula for the effective distribution width of PBL stiffened rectangular concrete-filled steel tubular joints considering the structural parameters of stiffeners were obtained.And the accuracy of the common formula was verified.