Study On Mechanical Behavior Of Opening Cold-Formed Thin-Wall C-Steel Combined I-Section Member Of Double-Limb

The cold-formed thin-walled C-shaped combined section steel member of double-limb has been wide applicability.But the existing experimental and theoretical researches about it have not achieved universal results.And the current relevant standards in our country have not stipulated design methods of the combined member.Therefore,it is urgent to explore the mechanical properties of such members and the influencing factors of its bearing capacity,and research a reasonable and reliable design method on the basis of former.The paper focused on the study on the mechanical performance of the C-shaped cross-section composite members of double-limb.The main work and achievements are as follows:(1)The finite element analysis of the mechanical performance of the double-limb C-shaped cross-section combined column was carried out through ANSYS.And on the basis of verifying the accuracy of the model,the buckling mode and stiffness changes were studied,and the influencing factors of its bearing capacity were also parameterized analyze.The result shows that the failure modes of the double-limb C-shaped combined column are local,distortion,global buckling and their related buckling.The compressive bearing capacity of the double-limb C-shaped combined column increases significantly with the increase of member thickness,flange width-to-thickness ratio and with the opening ratio of the plate decreases.But it decreases significantly with the increase of the slenderness ratio of the member and the porosity of the web.And the bolt spacing and opening spacing have little effect on the mechanical performance of the component.(2)Based on the existing test of the I-shaped steel beam of double-limb C-section,the paper used ANSYS to establish its finite element analysis model.And the paper analyzed its failure form and stiffness changes,and carries out a parametric analysis of its bearing capacity influencing factors.The result shows that the failure modes of the double-limb C-section combined steel beam established in the paper are the related buckling of local,distortion and global buckling.The flexural bearing capacity of the double-limb C-section combined steel beam increases significantly with the increase of member thickness,height and flange width.But it decreases with the increase of member length,span-to-height ratio and web opening ratio.And the bolt connection spacing and opening spacing of components have little influence on the flexural bearing capacity.(3)On the basis of summarizing the buckling mechanism of cold-formed thin-walled steel members,the calculation methods of bearing capacity of such members in Chinese and North American codes were compared.Based on the effective width method,the paper proposed a calculation method for the compressive and flexural bearing capacity of unopened and open-hole double-limb C-section combined members.The research result shows that: for the calculation of the bearing capacity of the split members,the direct strength method in the Chinese code and the North American code are conservative.However,the direct strength method is more accurate than the effective width method for the calculation of the bearing capacity of the split member.After verification,the proposed calculation method proposed in this paper is relatively reliable.