Post-fire residual strength and DSM-based predictions of cold-formed steel columns undergoing distortional collapse

Abstract This article aims to investigate the residual structural behavior, strength and Direct Strength Method (DSM) design of cold-formed steel (CFS) columns that fail in distortional modes after exposure to elevated temperatures from fire (post-fire conditions). It specifically examines the influence of temperature-dependent material properties of cold-formed steel on the residual strength of fixed-end lipped-channel (LC) columns after exposure to seven temperatures (T=20-300-400-500-600-700-800 ºC) and subsequent cooling, as reported in literature. Residual failure load data for the columns, obtained through ANSYS shell finite element analysis (SFEA), are employed to evaluate the impact of temperature-dependent steel constitutive models on the predictive accuracy of existing DSM distortional strength curves. The findings demonstrate that the current DSM distortional design curve for room temperature effectively addresses distortional failures in post-fire scenarios.