Study On The Static Performance Of Cold Bent Square Steel Pipe Column Joint Based On Self-tapping Screw Connection

In practical engineering,the self-tapping screw connection mode has high construction efficiency,certain shear resistance,and will harden the steel on the surface of the nail hole of the connected member,and improve the pressure bearing capacity.At the same time,the nail hole and screw close contact,its working performance is similar to the rivet,between the ordinary screw and friction type high strength bolt,closer to the friction type high strength bolt.Based on this,this paper proposes a new type of splicing node form: the self-tapping screw of cold-bent square steel pipe column is used to connect the splicing node,which is composed of two cold-bent square steel pipe and the filling plate outside the lap area or the inner casing by self-tapping screw.The structure of this kind of connection is simple,clear force transmission mode and widely used.Based on experiments,this article uses ABAQUS and theoretical analysis to study the static performance of cold formed square steel pipe column self tapping screw connection joints,and proposes corresponding bearing capacity calculation methods.(1)The tensile test and ABAQUS finite element simulation analysis were conducted on the self tapping screw assembly plate to verify the correctness and reliability of the modeling method in this paper.Due to the larger bearing capacity obtained from the calculation formula of the self tapping screw assembly plate using the Chinese standard(GB50018-2002)than the experimental value,a calculation formula for the shear bearing capacity of a single self tapping screw based on this plate thickness condition was proposed.(2)Tensile and bending tests were conducted on 10 sets of spliced node specimens and 7cold formed square steel pipe self tapping screw connection spliced columns.Parameter analysis was conducted on the material properties of cold formed square steel pipes,wall thickness of cold formed square steel pipes,diameter of self tapping screws,arrangement method,screw transverse distance,screw longitudinal distance,number of screw rows,number of screw columns,and construction form.The results showed that the diameter and number of self tapping screws had a significant impact on the tensile bearing capacity of the node.The diameter of self tapping screws The arrangement method,longitudinal distance of screws,number of screw rows and columns have a significant impact on the bending bearing capacity of nodes,and the use of inner sleeve construction can improve the bearing capacity of nodes.A calculation formula for the bearing capacity of cold formed square steel pipe self tapping screw splicing nodes is proposed,providing theoretical support for the calculation of the bearing capacity of such splicing nodes.(3)Finally,ABAQUS finite element simulation analysis was conducted on the spliced joints under the combined action of axial force and bending moment,to study their relevant performance under the combined action of axial force and bending moment.A design method for cold formed square steel pipe column self tapping screw connection spliced joints under the combined action of axial force and bending moment was proposed.