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Steel and Composite Structures
  Volume 40, Number 1, July10 2021, pages 75-85

Behavior of hybrid CFST with FRP-confined UHPC core under axial compression
Yi Tao, Jin-Ben Gu, Jian-Fei Chen and Peng Feng

    A fiber-reinforced polymer (FRP)-confined concrete core that provides high strength and ductility under axial compression can act as strength enhancement in a hybrid column. In the present study, ordinary concrete was replaced with ultra-high-performance concrete (UHPC) to form an FRP-confined UHPC core (FCUC). The FCUC was embedded in square concrete-filled steel tube (CFST) columns to form a high-performance hybrid column (SCF-UHPC column for short). The axial compressive behavior of the SCF-UHPC was experimentally investigated using 12 SCF-UHPC columns and two ordinary CFST columns for comparison. The advantages of the SCF-UHPC include excellent axial load-bearing capacity, good ductility, and stable residual load-bearing capacity. The results show that failure of an SCF-UHPC column was caused by FRP rupture of FCUC, which occurred after steel tube buckling that results in the degraded stiffness. It was also shown that the load-displacement behavior of the SCF-UHPC composite column was determined by the UHPC core diameter and the corresponding confinement provided by the outer steel tube and inner FRP jacket. A hardening effect could be achieved when the confinement demand of the UHPC core was satisfied, whereas a plateau effect appeared if the confinement was insufficient. Furthermore, the load-bearing capacity and ductility of the SCF-UHPC columns improved with increased thickness of the steel tube and the FRP.
Key Words
    FRP; UHPC; composite column; axial compression behavior; experimental study
Yi Tao: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, China;
State Key Laboratory of Green Building in Western China, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, China
Jin-Ben Gu: College of Civil Engineering, Tongji University, Shanghai, China
Jian-Fei Chen: Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
Peng Feng: Department of Civil Engineering, Tsinghua University, Beijing, China

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