Research Progress on Concrete-Filled Steel Tubes with Defects

Concrete-filled steel tube (CFST) structures are widely used in civil engineering due to their high load-bearing capacity and construction efficiency. However, core concrete defects such as voids and interfacial gaps significantly degrade mechanical performance, posing serious threats to structural safety. This paper systematically reviews influencing factors of CFST mechanical properties, load-bearing capacity calculation methods, and defect damage mechanisms. Studies indicate that cross-sectional shape (circular > square > polygonal), steel tube thickness, and material strength significantly affect axial compression performance. Void defects reduce load-bearing capacity by 18.5%–59% by disrupting the confinement effect, with near-wall voids causing 15%–20% greater losses than central voids. Secondary grouting and CFRP reinforcement restore 85%–92% and 10%–15% of capacity, respectively, but irreversible performance losses persist. Finite element models reveal conservative deviations (up to 20%) in current codes for thin-walled high-strength CFST columns. The study highlights higher defect sensitivity in non-circular sections, necessitating defect rate–capacity reduction coefficient tables. Future research should focus on multi-defect coupling effects, smart repair technologies, and refined computational models to enhance engineering reliability.