Flexural behavior of hybrid concrete-filled fiber reinforced polymer tube columns

Abstract

The concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) system has been widely studied as a durable alternative design for bridge columns. Research has shown that utilizing a small number of longitudinal steel bars in the concrete core provides the energy dissipation characteristics required for resisting extreme loads, such as seismic and blast. However, the construction complexity associated with the addition of rebar discourages the implementation of this system. In a novel approach, this study proposes and investigates the structural performance of CFFTs with a hybrid glass/steel fiber reinforced tube. This hybrid CFFT (HCFFT) system integrates the required longitudinal steel reinforcement into the FRP shell in the form of 30-µm fibers. This study details the experimental results from two CFFT and four HCFFT circular specimens tested under half-cyclic four-point bending. The effect of concrete slippage inside the tube was investigated. The flexural capacity, residual deformation, damage, and energy absorption capacity were experimentally evaluated. The HCFFT specimens exhibited higher energy absorption and lower degradations in stiffness compared to the CFFTs at comparable flexural deformations. Moment-curvature analysis was used to quantify the contribution of the concrete core when it is allowed to slide inside the tube.