Experimental Tests and Numerical Modelling on Slender Steel Columns at High Temperatures

Purpose
The purpose of this paper is to gain from experimental tests an insight into the failure mode of slender steel columns subjected to fire. The tests will also be used to validate a numerical model.

Design/methodology/approach
A series of experimental fire tests were conducted on eight full-scale steel columns made of slender I-shaped Class 4 sections. Six columns were made of welded sections (some prismatic and some tapered members), and two columns were made of hot rolled sections. The nominal length of the columns was 2.7 meters with the whole length being heated. The load was applied at ambient temperature after which the temperature was increased under constant load. The load was applied concentrically on some tests and with an eccentricity in other tests. Heating was applied by electrical resistances enclosed in ceramic pads. Numerical simulations were performed with the software SAFIR® using shell elements.

Findings
The tests have allowed determining the appropriate method of application of the electrical heating system for obtaining a uniform temperature distribution in the members. Failure of the columns during the tests occurred by combination of local and global buckling. The numerical model reproduced correctly the failure modes as well as the critical temperatures.

Originality/value
The numerical model that has been validated has been used in subsequent parametric analyses performed to derive design equations to be used in practice. This series of test results can be used by the scientific community to validate their own numerical or analytical models for the fire resistance of slender steel columns.