Compressive behavior of concrete-filled stainless steel tube stub columns post-fire

This study investigates the post-fire axial compression behavior of concrete-filled stainless steel tube (CFSST) stub columns, aiming to inform strategies for strengthening and retrofitting fire-damaged CFSST structures. The paper reviews the mechanical properties and fire resistance of CFSST, presenting results from a series of fire and axial compression tests conducted on 69 circular CFSST stub columns. Key parameters included fire exposure conditions, stainless steel tube wall thickness, concrete strength, and cooling methods. The analysis includes the failure mode, load-deformation relationship, ultimate bearing capacity, initial compressive stiffness, and ductility of specimens post-fire. The primary post-fire axial compression failure mode of the specimens was characterized by localized buckling uniformly distributed along the vertical axis. For fire durations of 60 min or less, the ultimate bearing capacity of the specimens was largely restored after cooling, with a bearing capacity loss of less than 10 %. Specimens subjected to water cooling exhibited lower initial compressive stiffness and ultimate bearing capacity compared to those cooled by air. Lastly, a formula is proposed for predicting the ultimate bearing capacity of CFSST stub columns following exposure to ISO 834 standard fire conditions.