On The Distortional Buckling, Post-Buckling And Strength of Cold-Formed Steel Lipped Channel Columns Under Fire Conditions

Abstract

This paper reports the available results of an ongoing shell finite element investigation on the distortional buckling, post-buckling and ultimate strength behaviour of cold-formed steel lipped channel columns (centrally compressed members) subjected to high temperatures typically caused by fire conditions. Two column collapse situations are dealt with, corresponding to different loading strategies: (i) application of an increasing compressive load to columns subjected to a constant (uniform) temperature distribution, in order to obtain failure loads, and (ii) application of a progressive temperature raise to axially compressed column, in order to obtain failure temperatures - the latter approach provides a more realistic simulation of fire conditions. The steel material behaviour at high temperatures is described by the constitutive model prescribed in Eurocode 3 for cold-formed steel. After validating the numerical model adopted, through the comparison with results of simulations reported in the literature and based on experimentally obtained stress-strain laws, the paper presents numerical results concerning lipped channel columns made of various steel grades under fire conditions - they consist of (i) non-linear equilibrium paths, yielded by steady state and transient column analyses, and (ii) the corresponding failure loads/stresses and temperatures.