Improving fire performance with steel fibers for internally anchored square composite columns

• Innovative idea of fabricating stiffened CFT columns – ACT columns.
• The ACT tube does not require an additional process for installation of stiffeners.
• A total of 8 full-scaled specimens were fabricated and Fire resistance tested.
• Reinforcing concrete with 0.375% steel fibers was found to be very effective.

This study focuses on mixing steel fiber in the concrete to improve the ductility and toughness of the columns. The purpose of the study is to evaluate the load capacity and deformation capacity associated with the amount of steel fiber and loading condition and to analyze the interplay between the steel fiber reinforced concrete and the welding built-up square tube in terms of structure and fire resistance performance. Reinforcement of concrete with steel fiber, when cross-section shape and boundary condition (load ratio) remained unchanged, improved fire resistance performance by 1.1–1.3 times. It is deemed that the area resisting thermal load increased and fire resistance performance was improved since the concrete reinforced with steel fiber restrained cracking. In addition, the fact that the cross-sections of the concrete were barely damaged indicates that load share capacity was greatly improved.