Experiments on perforated cold-formed built-up I-section beam-columns with longitudinal web and complex edge stiffeners

A built-up I-section with longitudinal web and complex edge stiffeners is expected to have better performance to resist against local and distortional buckling compared to built-up I-section without these. In this paper, the compression behavior of perforated cold-formed beams-columns with longitudinal web and complex edge stiffeners was experimentally studied between pined-ends. It contained 16 single section and 8 built-up section specimens, respectively. The above research was shown that the form of longitudinal stiffeners and built-up I sections could effectively improve steel utilization and load-carrying capacity. For the single-limb section, effective centroid shift led to an eccentricity of the applied force and hence induced the maximum ultimate load achieved at a certain loading eccentricity, but not at concentricity. However, the built-up member was symmetrical along the center of the member and uniformly compressed on both sides, which was not affected by the above. It was noteworthy that the two adjacent single-limb webs of conventional built-up I-section exhibited some specific support to each other, but the deformation of the plate around the hole cannot be restricted. However, the section with web stiffeners shown an opposite result of the above situation. Meanwhile, the longitudinal stiffener can obviously resist the built-up members' elastic deformation under the same condition. In addition, a finite element model was developed and verified against experiments of perforated beam-columns. Finally, two different Direct Strength Method (DSM) formulas were used to calculate the ultimate bearing capacity of perforated beam-column members under eccentric load. The calculated results were compared. It can be seen that the DSM formula that considered the distortional and overall relative buckling was closer to the actual value.