Fire resistance performance of welded built-up square CFT columns with reduced intumescent paint

Welded built-up square CFT columns are widely employed in construction field thanks to their structural efficiencies by avoiding stress concentration area and improving workability in fabrication and maximizing the composite effect enabled by bent ribs. Although welded built-up square CFT columns have structural advantages over other members and are widely used, they are classified as non-fire proof in Korea because the steel tubes are directly exposed to a fire. Thus, fire coating required for the columns by the law results in inefficient design. This study suggests welded built-up square CFT columns with reduced coating to enable improved fire-resistance performance for 2-3 hours. The purpose of the study is to analyse their fire-resistance performance using the variable of axial Load ratio which is the major factor in the performance and suggest efficient functional design with reduced coating.