The Study On Axial Compression Performance Of Cold-formed Steel Built-up Section Columns

The cold-formed thin-walled steel structure has been developed for more than 60 years.It is an energy-saving and space-saving green building which is suitable for the industrialization of residential buildings.It has the characteristics of light weight,short construction and suitable for the development of fabricated buildings.The development of cold-formed thin-walled steel structures is in line with China's national conditions and land resources policies,environmental protection policies and sustainable development strategies.In recent years,with the rapid development of cold-formed thin-walled steel structures,the structural forms of the buildings are diversified,and the stress conditions of the structures are also more and more complicated.Therefore,the biaxial cross-section members in the form of biaxial symmetry cross sections emerge as the times require.At present,the cold-formed thin-walled steel double-legged section column is mainly composed of two single-limb C-section members,which are rarely studied.In theoretical research,at present,the formula of direct strength method for the axial compressive bearing capacity of cold-formed thin-walled section steel single-section members has been put forward at home and abroad.Compared with the effective width method,this method is more simple and predictable The instability mode of the component.However,it is impossible to directly calculate the bearing capacity by using the method of direct strength method.Therefore,how to calculate the bearing capacity of built-up section members based on the direct strength method becomes an urgent problem to be solved.In this paper,a combination of experimental and theoretical methods to study the axial compression composite cross-section member performance.First of all,a total of 18 built-up section complex crimping channel,built-up E-shaped complex crimping channel,built-up V-shaped stiffened complex curling channel three kinds of splitting columns were subjected to axial compression test,The material properties of the steel,the actual size of the test piece,the initial defect,the stress-strain distribution,displacement and axial displacement at the central height section were measured and the ultimate bearing capacity and failure mode of the test piece were recorded.The test was simulated using ANSYS 12.0,a large,general purpose finite element program,and verified for accuracy.After verifying the correctness of the simulation method,the effects of self-tapping screw pitch,cross-section geometric parameters and slenderness ratio on the axial compressive performance and the flattening effect of cold-formed thin-walled steel built-up section columns were studied.The results show that the web stiffener can effectively enhance the bearing capacity of built-up section columns.Under the same geometrical parameters,the maximum load carrying capacity of built-up section ?-shaped complex curling channel steel columns is the maximum,Complicated crimping channel steel columns followed by the built-up section column minimum;web stiffened will affect the splitting effect of built-up section column,Limbs combined section stiffening cross-section column;two-legged cross-section column for the initial eccentricity is very sensitive to the initial eccentric can not be ignored;self-tapping screw spacing changes on the built-up section column bearing capacity and buckling mode has little effect;Will significantly change the bearing capacity of built-up section and buckling mode,but also will increase the bearing capacity of built-up section and affect the effect of splitting built-up section.Based on the experiment and finite element analysis,the calculation method of the ultimate bearing capacity of the column with built-up section is studied.Considering the splitting effect of single-limbed column and the reduction effect of I-shaped column,a practical method of direct strength method applied to axial compressive bearing capacity of built-up section colmun is proposed,and the applicability of the formula is verified.The formula obtained is Actual engineering application as well as the revision of the code.