Performance of single and built-up I-shaped cold formed steel stud under double sided walls fire exposure

Abstract

Light-gauge Steel Frame (LSF) walls are expanded nowadays due to several advantages, especially to achieve economy, sustainability and improved structural performance. The latter has stimulated designers to adopt Cold Formed Steel (CFS) members as primary components of LSF walls. However, the high thermal conductivity and slenderness of CFS sections make them vulnerable to mechanical degradation during fire. While numerous studies have investigated the performance of CFS stud walls under one-sided fire exposure, the investigation on double-sided fire exposure remains limited, especially for built-up studs. This study investigates the performance of CFS stud walls under compression loading, subjected to one-sided and double-sided fire exposure. Numerical models were developed using ANSYS APDL, considering geometric imperfections, material nonlinearities and contact element effect. The developed models were validated against previous experimental and numerical results. Various parameters were analysed through parametric study, including steel thickness and grades, web stiffeners and I-shaped stud configurations. The results demonstrate the significant impact of the double-sided fire exposure on CFS walls performance, reducing the fire resistance by 41 % and 50 % for CFS thicknesses of 1.15 mm and 1.5 mm, respectively, compared to one-sided fire exposure. Steel grade and I-shaped configurations were found to significantly enhance the load-bearing capacity and fire resistance of CFS walls. The maximum temperatures predicted for each load ratio were used to calculate the load ratio as per EN1993–1–2. New formulas, based on load ratio were proposed to predict the maximum temperature at failure for CFS walls subjected to one-sided and double-sided fire exposure. The findings will improve fire structural design codes of CFS walls, by ensuring accurate predictions of limiting temperatures and fire resistance and providing engineers with substantial data for LSF structures.