Performance of cold-formed C-sections reinforced by sleeves under concentric and eccentric compression

Abstract

This paper proposed and investigated the performance of cold-formed thin-walled steel open-section lipped channel columns reinforced with plain channel sleeve(s). The novel reinforcement strategy was intended to improve the post-distortional ultimate bearing capacity of the reinforced lipped channel columns. A total of 24 reinforced columns at four different lengths (400 mm, 1000 mm, 1600 mm, and 2200 mm) were tested under axial and eccentric loads. Initial geometric imperfections, load-displacement curves, load-strain curves, ultimate bearing capacity, and collapse modes from the experimental study were summarized and discussed. A finite element model was developed and validated against the experimental results. Then a total of 300 finite element simulations considering a variety of parameters, such as sleeve spacing, axial and eccentric compression about minor (y-y) and major (x-x) axis, and lip length, were performed and investigated. The results demonstrated the effectiveness of channel sleeves in restraining or inhibiting the occurrence and development of distortional buckling. The results were also evaluated with the current design provisions, such as the Effective Width Method in AISI S100–16, AS/NZS 4600, and EN1993-1-3, and the Direct Strength Method (DSM) in AISI S100–16. Finally, due to conservativeness in these methods, a modified design method based on DSM in AISI S100–16 was proposed.