Flexural strengthening of RC structural walls using EBROG method and FRP anchors: Experimental and analytical insights

A new flexural strengthening method for reinforced concrete (RC) structural walls is proposed in this study, involving the first-time integration of the externally bonded reinforcement on grooves (EBROG) technique with fiber-reinforced polymer (FRP) spike anchors. To assess the performance of this combined system, three walls were investigated under bidirectional cyclic lateral loading: one unstrengthened control wall (FCW) and two strengthened walls (FSW1 and FSW2). The FSW1 specimen was retrofitted using vertical EBROG FRP strips and anchors, while FSW2 included additional U-shaped strips and transverse FRP anchors to confine the boundary regions. Experimental results showed significant enhancement in performance: the lateral load capacity increased by 36 % in FSW1 and 61 % in FSW2 compared to FCW. The energy dissipation improved by 15.2 % and 32.6 % for FSW1 and FSW2, respectively. The average equivalent viscous damping ratio rose from 10.8 % in FCW to 12.6 % in FSW1 and 14.3 % in FSW2. Although the ductility index decreased from 4.4 in FCW to 2.7 in FSW1, it partially recovered to 3.3 in FSW2 due to enhanced boundary confinement. Theoretical predictions based on EBR guidelines underestimated the flexural capacity due to assumed FRP debonding limits. In contrast, the EBROG technique prevented debonding, allowing better utilization of FRP strength and resulting in higher-than-predicted capacities. The results demonstrate the capability of the EBROG method to enhance strength, energy dissipation, and damping capacity while preserving structural integrity, offering a practical solution for upgrading RC shear walls with limited flexural capacity under seismic conditions.