Research On Axially Compressed Behavior Of Quadruple-limbs Double Box Section Built-up Cold-formed Steel Columns

Quadruple-limbs double box section built-up cold-formed steel column is mainly structural member, which si composed of double C-sections and double U-sections connected by self-drilling screws.This paper mainly describes the detailed research on axially compressed behavior of the built-up column by tests and numerical analysis. The current standard is no calculation formula of the built-up section column, the corresponding proposed design method is proposed. Details are as follows:At first, the quadruple-limbs double box section built-up cold-formed steel columns are tested,include of axial compression specimens and eccentric compression specimens.Introduced the trial device, material test method, test phenomena and full test course as well as the analysis of test result etc in details.Secondly, using the finite element software ABAQUS to simulate the quadruple-limbs double box section built-up cold-formed steel column.The comparison of finite element analysis results and test results verified the correctness of the finite element model and method. For the variable parameter of factors, which effect the bearing capacity of the built-up columns,analysised by the finite element program,including slenderess ratio,web width-thickness ratio, eccentricity distance. The analysis results indicates that the slenderness ratio, eccentric distance and the width-thickness ratio have great effect on the ultimate bearing capacity of build-up cold-formed steel columns.Thirdly, axial bearing capacity and eccentric bearing capacity of the columns are caculated according to the GB50018-2002 and AISI2007(Effective Width Method and Direct Strength Method).Then the result caculated by standard is compared with the test results,the finite element analysis results.By analysis the comparison:for the axial compression specimens,the GB50018-2002 calculation of the long columnsare close to the results of the test,and the calculation of short columns is unsafe.The comparison show that the effective width method result and the direct strength method result is similar.But, the results calculate by AISI is unsafe. The results calculate by standard of the eccentric columns is conservative.Finally,based on the comparison of test results,finite element analysis results and standard calculation,modified calculate method which is suitable for quadruple-limbs double box section built-up cold-formed steel column under axial compression and eccentric compression is proposed.