Cyclic Behavior of Hybrid Columns Made of Ultra High Performance Concrete and Fiber Reinforced Polymers

Abstract

The unique features of ultra-high-performance concrete (UHPC) in damage tolerance, energy absorption, and deformability were combined with the superior performance of concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) to develop a novel hybrid system of FRP tube and UHPC, and the cyclic behavior of this system evaluated. Four specimens were tested. Two were steel-reinforced: one with conventional concrete (RC), and the other (RUHPC) with UHPC within twice the plastic hinge length and conventional concrete for the remainder of the column length. The other two had FRP tubes: one filled with conventional concrete (CFFT), and the other (UHPCFFT) filled with UHPC within twice the plastic hinge length and conventional concrete for the remainder of the column length. Each column was tested as a cantilever under a constant axial load and reverse cyclic lateral loads applied incrementally in displacement control. Each of the tubed specimens without any internal reinforcement achieved the same flexural strength and ductility as its steel-reinforced counterpart. Specimen UHPCFFT showed significantly higher flexural strength and initial stiffness, lower residual drift, and relatively similar energy dissipation as compared with Specimen RC. The proposed hybrid system can be optimized for strength and ductility as a viable alternative to the conventional RC column.