Axial behavior of slender reactive powder concrete-filled steel tubular columns confined by CFRP

Abstract

Reactive powder concrete-filled steel tubes (RPCFSTs) have become the focus of research in recent years owing to their ultra-high strength and good ductility. However, the steel tube in this type of member often exhibits an inelastic outward local buckling. The use of carbon-fiber-reinforced polymer (CFRP) can effectively suppress this outward local buckling and has shown great advantages in strengthening a new alternative structure. In this work, we conducted axial compression experiments to study the effect of slenderness ratio on the performance of circular RPCFST columns strengthened by CFRP. A total of 12 specimens were manufactured, and compression tests were conducted by varying the length of the members (800, 1200, and 1600 mm) and CFRP layers (0–3). The results showed that sufficient CFRP confinement can significantly improve the bearing capacity and ductility of the RPCFST columns. However, the confinement effect decreased with the increase in the slenderness ratio. We suggest a slenderness ratio of 40 and a three-layer CFRP-confined slender RPCFST column for engineering applications. Based on Euler’s theory for unified materials, a theoretical model for the elastic and elastoplastic instabilities of slender CFRP-confined RPCFST columns was proposed, and the calculation and experimental results were in good agreement.