Numerical evaluation of impact resistance of concrete columns reinforced with GFRP bars under various axial force ratios and impact velocities

Fiber-reinforced polymer (FRP) bars have the characteristics of high strength, lightweight, and corrosion resistance, which can be used as a substitute for conventional steel bars in a corrosive environment. A threedimensional (3D) model of the concrete column considering the dynamic increase factor of the concrete, steel bars, and FRP bars was developed using finite element (FE) method to investigate the difference of the concrete columns with steel bars and FRP bars in the impact behavior. The failure pattern, impact force, displacement, reinforcement strain, internal force, and energy of GFRP-RC and RC columns were compared. Then, the effects of the axial force ratio of 0-0.6 and the impact velocity of 1.2-5.6 m/s on the impact behavior were further discussed and an optimal axial force ratio was recommended in this study. The results showed that the impact force, internal force, and local deformation of the GFRP-RC column were slightly smaller than those of the RC column, but the duration and displacement increased. The increase in axial force ratio caused the concrete at the top and bottom of GFRP-RC columns to be crushed, whereas the impact resistance of GFRP-RC columns was best when the axial force ratio was 0.2. The more serious damage to the concrete occurred at the local impact position and both ends of the column as a response to the increase in the impact velocity. The concrete exhibited larger energy dissipation for GFRP-RC columns when subjected to different axial force ratios and impact velocities.