Development of a Calculation Method for the Fire Design of Concrete-Filled Steel Tubular Columns

Abstract

This paper presents a method for evaluating the fire resistance of concrete-filled steel tubular columns (CFST), developed in the framework of the European Project FRISCC. The aim of this project is to develop a full methodology that solves the shortcomings of the current design rules in EN 1994-1-2, proved unsafe for slender columns. For that purpose, two numerical models are developed and validated against the results of an extensive experimental programme. The numerical models are subsequently used for conducting a comprehensive parametric study. Based on the results of the parametric study, design rules for the evaluation of the fire resistance of CFST columns of different cross-section shape are developed, extending the applicability of the current code provisions. Innovative sections, such as elliptical hollow sections (EHS) are accounted for in the method. The design proposal is divided into two parts: a simplified cross-sectional temperature field assessment and a method for evaluating the ultimate buckling load in the fire situation, using the equivalent temperatures obtained from the previous step. The effect of eccentricity is evaluated through a modification in the method, which accounts for eccentricities on both minor and major axis, reaching large eccentricities of e/D = 1.