Fire resistance of concrete-filled cold-formed steel (CF-CFS) built-up short columns

• Published in: Journal of Building Engineering Vol. 48; p. 103854
• Main Authors: Rahnavard, Rohola, Craveiro, Hélder D., Simões, Rui A., Laím, Luís, Santiago, Aldina
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-05-2022
• Subjects: Built-up section; Cold-formed steel; Concrete-filled; Fire resistance; Heat transfer analysis; Thermal properties; Fire resistance; Thermal properties; Concrete-filled; Cold-formed steel; Built-up section; Heat transfer analysis
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2021.103854

The concrete-filled cold-formed steel built-up composite (CF-CFS) column is an innovative and versatile solution that may be used as an alternative structural element in construction. One of the main advantages of composite concrete-filled columns is their fire behavior, which has not been assessed for this specific solution (CF-CFS). Moreover, the available design codes for composite structures do not present a straightforward analytical procedure for concrete-filled cold-formed steel built-up columns. The present paper reports an experimental investigation on the fire resistance of four CF-CFS built-up columns. Twelve CF-CFS short columns were tested. The fire test setup, procedure, and results were fully reported and discussed, including the temperature evolution, load-temperature capacities, and load-deformation. A sequential thermal-stress finite element analysis (FEA) model was developed and calibrated against the test results. Experimental results were compared with design predictions according to the EN 1994-1-2 for composite steel-concrete sections, considering the simplified method (Annex H) and the general method. Moreover, the paper discussed the applicability of EN1994-1-2 to predict the fire resistance of the concrete-filled thin-walled CFS built-up composite columns. The results showed that the predictions according to the simplified design method (Annex H) tend to be highly conservative; but, the predictions based on the general method tend to provide slightly unconservative results, still requiring additional adjustments to improve its accuracy.
•Experimental investigation on the fire resistance of innovative concrete-filled cold-formed steel built-up short columns.•Buckling phenomena of concrete-filled cold-formed steel short columns.•A numerical model for understanding temperature evolution.•Design predictions according to the EN 1994-1-2.•Highly conservative predictions according to Annex H and slightly unconservative predictions based on the general method.