Experimental And Theoretical Research On Axial Compression Bearing Capacity Of Three Limbs Open Section Built-Up Cold-Formed Steel Columns

Cold-formed steel structures having a fast development recently, however there is rarely study on the built-up cold-formed steel columns at the home and abroad, which used as the maily bearing members of the cold-formed steel structures. The behaviors of three limbs open section built-up cold-formed columns of two different sections forms are researched in this paper.Firstly, this paper introduced the tests of three limbs open section built-up cold-formed steel columns detailedly; including the test contents, material properties, test device, test process, and then the results are analyzed in details.Secondly, the finite element program ANSYS10.0 is applied to implement the nonlinear analysis of axial compressed built-up cold-formed columns. Columns and screms are simulated by the Shell 181 and Soild 45 respectively. The comparison of FEM results and test results shows that they are agree well with each other.After that, three parameters—the slendness ratioλ, the screw-connection spacing, the maximum width-thickness ratio of plate, were simulated using ANSYS10.0, and then analyzed the effect of these parameters on the axial compression bearing capacity of three limbs open section built-up cold-formed steel columns. The analysis results indicates the slendness ratioλand the maximum width-thickness ratio of plate have great influence on the the axial compression bearing capacity of three-limbs open section built-up cold-formed steel columns than the screw-connection spacing.Subsequently, based on the test and the finite element no linear analysis, load bearing capacity of columns was caculated by the GB50018-2002, AISI2004 ("Effective Width Method" and "Direct Strength Method"). Then the results caculated by specification were compared with the test results and the ANSYS results. The comparision show that the GB50018-2002 could be used to calculate the he axial compression bearing capacity for the short columns and the middle-long columns, but it is conservative for long columns.Finaly, based on the analysis and the comparision, three calculation methods for the the axial compression bearing capacity of three-limbs open section built-up cold-formed steel columns are investigated and recommended the calculation methods for designing and engineering.