Behaviors of FRP confined rectangular concrete-filled thin-walled steel tubular stub columns using high-strength materials under axial load

Rectangular concrete-filled thin-walled steel tube (CFT) columns using high-strength steel and concrete are susceptible to local buckling, which will weaken the constraint effect and reduce the advantages of high-strength materials. Fiber reinforced polymer (FRP) has favorable mechanical properties, which can be used to delay or even prevent the outward buckling of steel tube. This paper presents the experimental and theoretical study on axial compressive behavior of FRP confined concrete-filled thin-walled steel tube (FRP-CFT) stub columns with high-strength materials. The test variables included the aspect ratio of section, concrete strength and the layers of FRP, etc. Results show that the confinement of FRP delays the local buckling of steel tubes and increases the restraint strength of core concrete. The ductility of high-strength concrete is also improved. Based on the su-perposition theory and the effective width theory, this paper proposed the design approach to calculate the ultimate compressive resistance, considering the effect of local buckling of thin-walled steel tube and the confinement of the FRP. The design approach was verified with experimental results and can be used in practice.