Torsional Response of Cold-Formed Members Under Shear and Axial Forces: Experimental Evidence

It is well-known that torsional effects play a crucial role in the structural response of cold-formed steel members when subjected to eccentric transverse loads. However, torsion is often neglected in design practice when members are loaded axially, especially. This paper presents an experimental investigation on the torsional response of cold-formed members subjected separately to shear forces and to concentrated axial forces. An experimental campaign was carried out on full-scale specimens using dedicated test setups that allowed the isolated application of each loading condition. Displacements and internal stresses were monitored throughout the tests. To investigate the experimental outcomes and further exploit the topic, finite element models were also developed. As expected, the tests under shear loading confirmed the significant and detrimental influence of torsion on the global response. More importantly, the experimental results revealed that pronounced torsional deformations can also develop under eccentric axial loading, highlighting critical behavior that is commonly overlooked. The observed torsional response under axial forces was found to be strongly dependent on load eccentricity and cross-sectional geometry. The experimental evidence demonstrates that torsion represents a detrimental mechanism not only under shear forces but also under eccentric axial loading, emphasizing the need for its explicit consideration in the analysis and design of cold-formed steel members.