Behaviour and strength of unlipped channel sections under combined bending and torsion

Cold-formed steel unlipped channel sections are commonly used as bearers in floor systems. The loads from the joists are commonly transferred through the flanges or webs of the channel section bearers and not through their shear centre. Therefore, channel section bearers are subjected to combined bending and torsion, resulting in re-duced bending capacity. This research study has thus investigated the behaviour of thick unlipped channel sec-tions under combined bending and torsion using validated finite element models of beams with an eccentric concentrated load at mid-span. The member moment capacities of unlipped channel sections were obtained from idealized finite element models under uniform bending and with equivalent web and flange distributed forces for bending and torsion. First yield torques and combined bending and torsion capacities of unlipped chan-nel sections were obtained from finite element models validated using available experimental results. A numer-ical parametric study was also performed for currently available unlipped channel sections using validated finite element models and member moment capacities, combined bending and torsion capacities and first yield torques of unlipped channel sections were obtained. Two-separate bending-torsion interaction equations were proposed for positive and negative eccentric loading cases. (c) 2021 Elsevier Ltd. All rights reserved.