Research on axial compression behavior of cold-formed triple-lambs built-up open T-section columns

In this study, a total of 18 cold-formed built-up T-section (CFBUT) columns with two sectional dimensions and three length types were tested under uniaxial compression. The failure mode, ultimate strength and load-uniaxial displacement curve of the specimens were investigated. The test result shows that the main failure modes of long columns (LC), short columns (SC) and intermediate long column (MC) were flexural-torsional buckling mode, distortional buckling mode as well as flexure-torsional buckling mode, respectively. Subsequently, parametric analyses were conducted on the investigated specimens using the finite element analysis. The influences of the slenderness ratio and the web depth to plate thickness ratio on the mechanical behavior of the CFBUT columns were studied. Finally, the validation and accuracy of the effective width method in both Chinese design code GB50018-2002 and American code AISI-2007 and the direct strength method in AISI-2007 were evaluated for the CFBUT columns by using both the test and numerical results. The comparison results show that the prediction results obtained by adopting the two methods in both Chinese and American specification for LC, MC and SC-90 type specimen were rather conservative. However, for the SC-140 type specimen, the prediction difference between the experimental and calculation results obtained by adopting the two methods in both Chinese and American specifications can be controlled within 15%.