Experimental investigation on the seismic performance of FRP wrap confined FRP reinforced concrete columns

This article represents an experimental examination on the seismic performance of fiber reinforcement polymer (FRP) warp confined FRP reinforced concrete (FCFRC) columns. A total of six specimens were prepared, among which four specimens were confined with GFRP sheets in their plastic hinge regions, and the other two were left unconfined. Each specimen was tested under a combination of constant axial load and cyclic lateral displacement load. The main objective of this experimental study was to investigate the effect of hoop spacing and the effect of confinement layers of GFRP wraps applied at the plastic hinge zone on seismic performance. The confinement effect of FRP hoops and wraps on the seismic performance of the columns was evaluated in terms of failure modes, hysteresis behavior, skeleton curve, residual drift ratio, and energy dissipation capacity. The experimental results revealed that employing the GFRP wraps in plastic hinge regions effectively improved the load bearing capacity by 52.9%, energy dissipation capacity 3.6 times, and stiffness degradation of specimens, hence improving the seismic performance. It also had a positive impact on the residual drift ratio of FCFRC columns, which decreased by up to 75%. Additionally, decreasing the hoop spacing was also found effective in improving the seismic performance of the structure.