Seismic experimental research on damaged resilient reinforced concrete columns retrofitted by FRP sheets

The post-earthquake repairability was an attractive advantage of reinforced concrete (RC) frame structures with resilient RC (RRC) members. This paper investigates the seismic behavior of six RRC columns repaired with different fiber-reinforced polymer (FRP) types, the number of FRP layers, and additional steel plates. The results indicate that all original RRC columns exhibited a drift-hardening behavior before the drift ratio reached 3.0 %, while the residual drift ratio was less than 0.5 %. FRP-repaired RRC columns can achieve even higher peak strength than the original columns and effectively control their residual deformation. The increase in the number of carbon FRP (CFRP) layers leads to a decrease in residual displacement, while the type of FRP has no significant effect. Compared with the Aramid FRP-repaired column, the CFRP-repaired column showed higher initial stiffness and lower stiffness degradation rate. The FRP-steel plate repaired columns showed the highest initial stiffness and energy dissipation capacity. A simplified model containing two yield points was proposed to evaluate the residual displacement of the repaired RRC column referring to the FEMA’s recommendation which was based on the displacement at steel bar yield. In addition, a bilinear skeleton model curve based on a simplified hysteresis loop rule was proposed to predict the hysteresis behavior of the repaired RRC columns. • Seismic behavior of repaired resilient RC columns was investigated first. • Drift-hardening and self-centering behavior were observed in all repaired columns. • Lateral force and stiffness of damaged columns were approximately fully restored with bonded steel and FRP sheets. • A simplified hysteresis loop and residual deformation model were proposed.