Research On Axially Compressed Behavior Of Double Limbs Box Section Bulit-up Cold-formed Steel Columns

Double limbs box section built-up cold-formed steel column is composed of a C-section and a U-section member connected by self-drilling screws at the flange. In this article, the axially compressed behavior of the columns is reaserched by experiment and finite element analysis, the suggested calculation method of the bearing capacity of the axially compressed and the eccentric compressed columns in the current specification is proposed. Details are as follows:(1) A lot of double limbs box section built-up cold-formed steel columns are tested, include of axial compression specimens and eccentric compression specimens.Introduced the test devices, test method, test process, the failure mode, etc in details. Then the test results are analyzed and compared.(2)Using the finite element software ABAQUS to simulate the experiment. Set up the finite element models of double limbs box section built-up cold-formed steel columns that considering geometric nonlinearity, material nonlinearity and contact nonlinearity. The comparison of finite element analysis result and the test results shows that they are agree well with each other. It verified the validity of the finite element model.(3)The parametric analysis was carried out to slenderness ratio, the ratio of web height to thickness, and eccentric direction and eccentricity. The results of the analysis indicate that the ultimate bearing capacity of the columns will decrease with the increase of slenderness ratio and the ratio of web height to thickness, different eccentric direction and eccentricity will also caused great impact of the ultimate bearing capacity and failure modes of columns.Finally, the ultimate bearing load of test specimens and the finite element parametric analysis specimens are calculated by Chinese standard GB50018-2002 and AISI2007. Then the calculated results are compared with test results and finite element analysis results. By analysis the comparison, based on the calculation method of the Chinese standard, calculation method which is suitable for double limbs box section built-up cold-formed steel columns under axial compression and eccentric compression is proposed.