Temperature-induced instability in cold-formed steel beams with slotted webs subject to shear

Abstract

Cold-formed steel (CFS) is an emerging construction material that has been gaining momentum over the past few years. While the behavior of structural members made of CFS has been extensively studied at ambient conditions, the performance of these members under extreme events such as that associated with fire, is yet to be understood. In order to bridge this knowledge gap, this paper presents outcome of numerical studies aimed at understanding fire response of CFS beams. More specifically, this study explores the effect of temperature-induced shear-based instability on response of C-shaped CFS beams with slotted webs. For studying this phenomenon, a three-dimensional nonlinear numerical model is developed using the finite element (FE) simulation environment; ANSYS. The developed FE model is designed to incorporate temperature-dependent material properties as well as to account for unique geometric features and restraint conditions, as to accurately trace thermal and structural response of CFS beams. Once validated, the developed model was utilized to examine the effect of a number of factors namely; channel depth, web perforation pattern, as well as boundary conditions, on temperature-induced buckling susceptibility of CFS beams. The obtained results showed that these examined factors can significantly affect shear response of CFS channels with slotted webs at elevated temperatures. Findings observed from FE simulations were also shown to agree with that obtained from especially derived design expressions that give due consideration to geometric features and temperature-dependent material properties of slotted webs. This study concludes that in order to accurately capture the response of fire-exposed CFS beams, an accurate presentation of geometric and material features in such members is essential.