Benefit of Ultra-High Strength Infill in Concrete-Filled Steel Tubular Columns

Concrete filled steel tubes (CFST) represent a composite building member suitable especially for the construction of columns of a skeleton frame. Filling the steel tube with concrete allows the use of suitable properties of both materials and their interaction. This is very beneficial in a fire exposure, where a circular column has slightly better fire resistance than a square column. In case of an assessment of columns at the ultimate limit state (ULS), a buckling resistance decides. In previous research, it was found that increasing the strength of concrete increases buckling resistance only to a certain extent. The main aim of the article is to show through a theoretical study what benefit the use of ultra-high strength concrete has for buckling resistance of CFST.