Research On Axially Compressed Behavior Of Triple-limbs Half-open Section Built-up Cold-formed Steel Columns

Cold-formed steel built-up columns refers to a column which use the basic building blocks(including C-shaped, U-shaped, etc)by tapping can be connected with the self-drilling screws, with a variety of cross-sections form of bearing component. With the development of science and economy, cold-formed steel structures have been widely used in China’s construction industry. This paper is researched on the axial compression test and the axial compression theory and the eccentric compression theory of the triple-limbs half-open cold-formed section built-up cold-formed steel columns. Specific work content is as follows:First, studying two different sectional dimensions of the triple limbs cold-formed steel built-up columns with half-open sction. In the test, it mainly introduced the specimen cross-section forms, sizes and materials, test apparatus, methods of sensor placement and content of the specimentsand damage characteristics, then analyzed and compared the final test results in detail.Secondly, using the ABAQUS nonlinear finite element simulation software simulates all the beams with the actual size. When used the ABAQUS to simulate the columns, it chosen four-node reduced integrated shell element(SR4), selected mode by eigenvalues buckling analysis, using scaling factors to bring in the initial imperfections, then reach the ultimate bearing capacity by nonlinear buckling analysis, after that comparing finite element simulation and experimental results for both is consistent.Thirdly, by varying parameter analysis method, using ABAQUS finite element program to simulate the bearing capacity of cold-formed steel built-up columns to research the affect of major factors. The axial compression members studied the effect of slenderness ratio and web depth-thickness ratio on the ultimate bearing capacity; the eccentric compression members studied the effect of eccentric throw on the axial compression bearing capacity.Fourthly, it calculated the axial compression bearing capacity and eccentric compression bearing capacity according to China specification(GB50018-2002) and United States specification AISI2007 in the provides of method(“effective width method”and “directly strength method”), then compared the calculation results, test results, and finite-element analysis results, the result showed that: the “directly strength method ”calculation results and test results compared close, the“effective width method ”in specification of China and United States are more conservative.Finally, on the based of theoretical calculation and test research and finite-element analysis, the paper propose a modified calculation methods to calculate the axial compressive bearing capacity and the eccentric compressive bearing capacity of the triple limbs cold-formed steel built-up columns with half-open sction which is based on the theoretical calculation, test results and data analysisof finite-element.