Compression Tests And Theoretical Research Of Open Section Built-up Cold-Formed Steel Stub Columns

Built-up section cold-formed steel column is widely used in cold-formed steel housing system at home and abroad. In order to study its mechanical behavior and put forward a design proposal, the compression tests and theoretical research on open built-up section cold-formed steel stub columns and their basic conponent single-C and single-U stub columns are carried out in this paper.Firstly, the open built-up section cold-formed steel stub columns and their basic conponent are tested. It contains test process, mechanical behavior. And the question how to calculate the local buckling critical stress and load of open built-up section cold-formed steel compression stub columns has been discussed. In addition, the result states that the open built-up section cold-formed steel stub columns'ultimate load is neally equal to the superposition of their basic conponent's ultimate load.Secondly, ANSYS is applied to stimulate the buckling behavior and post-buckling behavior of members, and CUFSM is applied to stimulate the buckling behavior further. Then, on the basis of the accuracy of models, the screw spacing and width-thickness ratio are analyzed by ANSYS and CUFSM, and the result states that width-thickness ratio has great effect on the buckling and ultimate bearing capacity of open built-up section cold-formed steel compresstion stub columns and their basic conponent.Thirdly, the local buckling coefficient of open built-up section cold-formed steel compresstion stub columns and their basic conponent are back calculated by CUFSM, and put forward the calculated method of local buckling critical load for open built-up section cold-formed steel compresstion stub columns, and the percentage error is all below 5%.Finally, after briefly introducing the effective width method widely used, a new method in the field of cold-formed steel named Direct Strength Design Method is introduced in this paper. And the theory results are unconservative compared with test. Therefore, on the basis of our criterion, a new method is proposed:the ultimate bearing capacity of open built-up section cold-formed steel compresstion stub column=ηx the ultimate bearing capacity of its basic conponent, andηis different accocrding to the built-up section.To the open built-up section stub columns in this paper,η3=1.916,η6=2.756,η10=4.083. Meanwhile, the local buckling coefficient is taked according to the CUFSM modified back calculation, and the comparison of test results and the results calculated by the new method shows this method is reliable.