Effects of nonlinear elevated temperature stress-strain characteristics on the global buckling capacities of cold-formed steel columns

Abstract

Losses caused by the recent fire incidents are demanding proper fire safety regulations and fire protection measures around the globe while construction cost and call for environmental protection are increasing. The expansion of cold-formed steel (CFS) construction to mid-rise buildings in recent times has therefore identified the need for the accurate prediction of the load bearing capacities of CFS columns in fire. Despite several useful studies on the compression capacities of CFS columns at elevated temperatures, effects of nonlinear elevated temperature stress-strain characteristics on the global buckling capacities of CFS columns have not been investigated yet. In this research, the effects of nonlinearity between proportional limit stress and yield strength, strain hardening between yield and ultimate strengths and varying yield strength to Young's modulus ratio on the capacities of pinned and fixed ended columns subject to flexural-torsional and flexural buckling were investigated using a detailed numerical parametric study involving 1320 finite element analysis results. The accuracy of current CFS design standards, such as AS/NZS 4600, AS 4100 and EC3 Part 1–2, in predicting the elevated temperature global buckling capacities was investigated, and new design rules were proposed for Australian and European standards.