Local Buckling Behaviour of Steel Sections Subjected to Fire

Abstract

The local buckling behavior of steel sections subjected to fire is strongly affected by the nonlinear stressstrain relationship of steel at elevated temperatures, non-uniform temperature distributions as well as thermal strains and stresses. This paper proposes a strain-based calculation model found to be particularly suitable for analyzing the load-carrying behavior of steel members subjected to local buckling and fire. This model uses strain-based capacity curves – based on a plastic mechanism and results of a comprehensive numerical parametric study – for calculating the load-shortening behavior of stiffened and unstiffened elements (internal compression parts and outstand flanges) under fire conditions. Additionally, the model takes into account thermal strains and stresses during heating in fire as well as uniform and nonuniform temperature distributions. Strain-based models avoid classification of cross-sections and consider local buckling even for compact cross-sections. The strain-based calculation model accords well with results obtained from a parametric study using the finite element approach.