Study On The Force Performance Of Cold-formed Thin-walled Steel Double-limb Spliced Members With Hybrid Connection

The cold-formed thin-walled steel members are connected by basic units with selftapping screws,and they are widely used in keel frame,wall corners,door and window openings reinforcement and other supporting structures because of their various crosssectional forms and good force performance.In order to improve the axial compression stability of the members and enhance their bearing capacity,the existing research mainly adopts changing the cross-sectional form,adding steel links,adding embellishment sheets in the web,ring hoop reinforcement,CFRP reinforcement,etc.In the deformation phase of the structure,the deformation between sheets increases after the member flexes,and the shear resistance of the connection has a greater impact on the load capacity of the member.Selftapping screws were the most commonly used connectors for the connection of members,with high shear bearing capacity and easy to assemble,but in the large deformation stage of the structure,shear was easily tilted and then pulled off the damage,which was not conducive to further bearing of the members.In order to enhance the stability of the deformation phase of the assembled members,this paper adopted a hybrid connection of self-tapping screws and blind rivets for the assembly of double-limb open type members,and further studied the influence law of the connection on the stability of the assembled members through comparative tests.The main work carried out is as follows:(1)A method to improve the axial compression stability of cold-formed thin-walled steel splice members was proposed.The ultimate load capacity of the members was improved by changing the connectors of the splice members,i.e.,using a hybrid of self-tapping screws and blind rivets to connect the splice members to restrain the inter-slab deformation in the postbuckling deformation phase of the members.(2)The difference between the shear performance of the hybrid connection and that of a single self-tapping screw was investigated,and it was verified that the hybrid connection of rivets and self-tapping screws could effectively restrain the inter-sheet deformation on the basis of the joint load capacity,and the influence of the sheet thickness,sheet thickness ratio and the arrangement of the fasteners on the shear performance of the hybrid connection of rivets and self-tapping screws was analyzed,and the shear load capacity calculation method of the hybrid connection was established.(3)Two types of composite members with hybrid connection arrangement were designed,and the axial compression performance of the specimens was investigated by axial compression tests,and the influence of the spacing of the connections and the length of the members on their buckling mode,post-buckling strength and axial compression load capacity was discussed.(4)A comparison of the differences in the axial compression performance between the self-tapping screw-connected members and the hybrid-connected members reveals the influence of the hybrid connection on the axial compression stability of the members.The applicability of the calculation method of the bearing capacity of the axial compression members in the current code to the hybrid connection of the composite members was discussed through the comparison of the test value and the calculated value.