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

In this paper, double Limbs Closed Section Bulit-up Cold-formed Steel Column is composed of double C-sections connected by self-drilling screws and two 75 mm wide strips,which is 75 mm wide.This paper is researching their mechanical behavior under axial compression and eccentric compression conditions,by pressure test, nonlinear finite element and theoretical calculation. Specific work content is as follows:First, the double Limbs Closed Section Bulit-up Cold-formed Steel Columns(140 series) were tested, including axial compression specimens and eccentric compression specimens.There are 15 specimens in total, including long, medium and short three lengths. In the test, it detailed introduced the specimen cross-section forms, sizes and materials, test equipment, loading system,measuring points, gathered and analysised the results of the tests.Secondly, On the basis of the tests, using the ABAQUS nonlinear finite element simulation software completely true simulated all of the Specimens. Then,comparing the finite element simulations and Experimental results. Two results were in goodagreement, which verify the correctness of finite element modeling methods.Thirdly, finite element analysis of variable parameters: there are two specifications specimens,which is 90 series and 140 series. Using the same modeling methods previously, by changing the length of specimen,the thickness of cross-section,and the position of loading point,to Explore the effects of slenderness ratio, the web thickness ratio, the eccentric direction and the eccentricity to the axial force performance of double Limbs Closed Section Bulit-up Cold-formed Steel Columns. The results showed that slenderness ratio and web thickness ratio have greate impact to axial compression force performance of double Limbs Closed Section Bulit-up Columns; eccentric direction and the eccentricity have greate impact to biasing compression force performance of double Limbs Closed Section Bulit-up Columns.Fourthly, calculated the axial compression bearing capacity and eccentric compression bearing capacity according to the―effective width method‖ of China thin steel specification(GB50018-2002), ―effective width method‖and ―directly strength method‖of United States thin steel specification(AISI-2007).Then compared the calculation results with test results, and finite-element analysis results. The result showed that: compared with the Experimental results, the chinese specification algorithm was not completely safe, while the US specification algorithm was safe; compared with finite-element analysis results, standardized algorithm was too conservative.Finally, on the based of abundant finite-element analysis and theoretical calculation,the paper amended Existing norms algorithm,and propose a suitable calculation methods to calculate the axial compressive bearing capacity and the eccentric compressive bearing capacity of the double Limbs Closed Section Bulit-up Cold-formed Steel Columns.