Experimental investigation on the fire behaviour of rectangular and elliptical slender concrete-filled tubular columns

• Fire tests on elliptical and rectangular slender concrete filled tubular columns are presented.
• Concentric and eccentric loads in both minor and major axes are considered.
• Large relative eccentricities up to 0.5 are reached.
• The influence of cross-section shape, load eccentricity and percentage of reinforcement is investigated.
• The current design rules in EN1994-1-2 are evaluated for elliptical and rectangular sections.

While the fire behaviour of concrete-filled steel tubular (CFST) columns with circular and square cross-section has been well established based on experimental programs and numerical investigations, the information about the fire behaviour of CFST columns with rectangular or elliptical cross-section is very scarce. Therefore, further research is needed in order to establish the structural behaviour of concrete-filled elliptical and rectangular hollow sections at elevated temperatures as a basis for the future development of new design guidance. In this paper, a series of slender CFST columns of rectangular and elliptical cross-section are tested at elevated temperatures under both concentric and eccentric loads, reaching large eccentricities. The effect of the load eccentricity and percentage of reinforcement is studied, considering both major and minor axis buckling. The influence of the cross-section shape, load eccentricity and percentage of reinforcement on the fire behaviour of these columns is investigated. The experimental results are subsequently used to assess the current design rules in Eurocode 4 Part 1.2 for these new section shapes.