Experimental And Theoretical Research On Compressed Behavior Of Quadruple-Limbs Open Section Cold-formed C Steel Built-up Columns

Quadruple-limbs built-up open section cold-formed thin-wall C steel column is composed of four C-section members connected by self-drilling screws.In this article,in order to study the axial behavior of quadruple-limbs built-up open section cold-formed thin-wall C steel columns,destructive experiments and finite element analyses of different columns which had different lengthes(slenderness ratio)were conducted.There are no clear design articles on built-up section columns in the current specification,so the corresponding suggested correction method of the bearing capacity of the axially compressed and the eccentric compressed columns in the current specification is proposed.Firstly,destructive experiments of the single C-section and Quadruple-limbs built-up open section cold-formed steel columns under eccentric comprssion were conducted,the trial specimens,specimen property,trial device and test method are introduced in details,then test course and the failure mode full as well as ultimate bearing capacity were obtained.Secondly,finite element program ABAQUS is applied to implement the experiment.Finite element analysis involving contact nonlinearity,geometric nonlinearity,material nonlinearity is used to simulate test models under axial load.The comparison of finite element analysis result and the test results verified the validity of the finite element numerical simulation method.Subsequently,the variable parameters of factors which affect the bearing capacity of built-up section column were analysised by the finite element program.For Quadruple-limbs built-up open section cold-formed thin-wall C steel columns,the impact of slenderness ratio,web height thickness ratio and spacing of self-drilling screw on the axial bearing capacity of the columns were researched in detail;the impact of slenderness ratio,eccentric direction and eccentricity on the eccentric bearing capacity of the columns were also researched in detail.After that,the ultimate load bearing capacity of the section columns were caculated by GB50018-2002 and AISI2007(“Effective Width Method”and“Direct Strength Method”)And then the results caculated by specification were compared with the test results and the finite element analysis results.Finally,based on the the comparision and analysis of the results caculated by specification,the test results and the finite element analysis results,the design methods for the compression bearing capacity of quadruple-limbs built-up open section cold-formed thin-wall C steel column are investigated.And based on the calculation method of the Chinese standard and the principle of the ease of use of engineering designers,modified calculation methods is prosposed to calculate the axial bearing capacity and the bias bearing capacity of built-up section columns.