Fire design of stainless steel columns with hollow circular and elliptical sections

Abstract

One of the advantages of stainless steel is its better behaviour under elevated temperatures when compared to the conventional carbon steel, which can be important for structural applications where the fire action should be considered. The second generation of Part 1–2 of Eurocode 3 (prEN 1993-1-2:2021) proposes new calculation formulae resulting from studies on profiles with I-sections. However, it is still important to evaluate the accuracy and safety of the same formulae for columns with circular and elliptical hollow sections (CHS and EHS respectively), whose application in stainless steel structures is common. Hence, this work presents a numerical parametric study on the fire resistance of columns subjected to axial compression, with CHS and EHS, considering different stainless steel grades, cross-sections and member slendernesses, and elevated temperatures. The ultimate load capacities of the columns are obtained by geometrically and materially nonlinear analyses including imperfections, using the SAFIR finite element program and considering the constitutive law based on the two-phase Ramberg-Osgood formulation proposed in prEN 1993-1-2:2021. Based on the comparisons between the numerical results and the methodology of prEN 1993-1-2:2021, small suggestions are proposed to improve the fire design formulae for the cases of CHS and EHS profiles subjected to axial compression.