Structural behaviour and design of cold-formed steel floor systems

Cold-formed steel unlipped channel sections are commonly used as bearers in floor systems with RHS joists and different joist to bearer connections. These cold-formed steel sections are vulnerable to web crippling due to their higher width to thickness ratio. The applied loads and support reactions are transferred to channel section bearers away from their shear centre due to the commonly used connections, which lead to torsion in the sections. Therefore, the channel sections are subjected to combined actions of web crippling, bending and torsion in cold-formed steel floor systems.


The structural behaviour of unlipped channel sections subject to combined web crippling-bending and combined bending-torsion was investigated using finite element analysis. The first yield torques, bending and member moment capacities of unlipped channel sections were determined from validated finite element models using past test results. New combined web crippling-bending and combined bending-torsion interaction equations were proposed based on finite element analysis (FEA) results. The effects of different connections on the ultimate and serviceability loads of unlipped channel sections were also investigated. Suitable connections were proposed for the improved performance of unlipped channel section bearers in the floor systems based on test and FEA results.