Alternative approach to buckling of square hollow section steel columns in fire

Abstract

Stability of axially loaded steel columns with square hollow sections at elevated temperatures is studied herein. At present the Eurocode model for checking buckling capacity of columns in fire has been developed on the similar basis as for ambient conditions. It is shown that due to the effect of complex non-linear behavior the standard design model is not always adequate and in certain situations prediction of buckling capacity of columns according to the common design formulas may even reach results on the unsafe side. The main focus of this work is the performance of an analytical model against advanced numerical methods. For this purpose extensive numerical study was performed using non-linear FE method. Based on the results obtained with advanced calculation models of column behavior at elevated temperatures an analytical model has been proposed and verified. The proposed model accounts for variable non-linear stiffness properties, which have significant effect on the buckling capacity of axially loaded columns in fire. The advantage of the method is the format, which is convenient for incorporation into common design algorithms.