Effect of Partial Closing of the Open Face of Cold-Formed Steel Channel Sections

This document presents the effect of partial closing of the open face of cold formed steel channel. From the past, closed sections are favourably used in CFS for framing applications. Open sections, like channels offer good moment resistance and also offer a clean and flat surface on the outside of the web but when loaded in vertical direction cause twist in the channel section since the loading is not through the shear centre. This twist also causes lateral deflection of the section at the level of the two flanges. In order to restrain and minimize the lateral torsional bucking, an experimental and numerical trial has been performed on the channels which are covered with plate along the length of the beam by 1/3rd, 2/3rd and full cover plate of the beam channel and compared. Specimens with 2/3rd and full length cover plate along the length show improved resistance against lateral deflection and torsion. The performance reduces as length of the beam increases. The specimens of 2/3rd length cover plate show almost equal performance to the specimens of full length cover plate. As a result, 2/3rd cover plate beam can be efficiently used to serve the purpose for better efficiency. Numerical models are developed and compared with the experimental results. Following a series of analyses, it is found that in general, the effect of the covering is more significant on longer specimens. Conclusions derived based on the experimental and numerical results also point to the definite improvement by the partial closing of the channel sections. © 2021, The Institution of Engineers (India).