Experimental And Theoretical Research On Bearing Capacity Of Closed-section Multi-limbs Built-up Cold-formed Steel Compression Columns

Based on consulting a lot of documents, detailed result on the mechanics capability of closed-section multi-limbs build-up cold-formed steel columns by axial compression tests and the finite-element method calculation are presented in this paper.At first, closed-section two-limbs and closed-section four-limbs build-up cold-formed steel compression columns are tested, and introduced the test device, test methods, the test process and the result are analyzed in details.After that, the finite element program ANSYS 10.0 is applied to implement the nonliear analysis of axial compressed closed-section multi-limbs build-up cold-formed steel columns. The comparison of FEM results and test results show that they are agree well with each other. At the same time, the parameters of slendness ratio, screw-connection space, width-thickness ratio are analyzed by ANSYS. The analysis results indicates that the slenderness ratio and the width-thickness ratio have great effect on the ultimate bearing capacity of build-up cold-formed steel columns.Subsequently, based on the test and the finite element nolinear analysis, load bearing capacity of columns are caculated by the GB50018-2002, AISI2004 ("Effective Width Method"and"Direct Strength Method").Then the results calculated by specification are compared with the test results and the ANSYS results.The comparisons show that the ultimate bearing capacity of closed-section two-limbs built-up cold-formed steel columns calculate by specification is conservative, but it is unconservative for closed-section four-limbs built-up cold-formed steel columns.Finally, based on the analysis and the comparison, a modified calculation methods is prosposed to determine the ultimate bearing capacity of closed-section multi-limbs built-up cold-formed steel columns.