Effect of Interfacial Bond on Plastic Hinge Length of FRP-Confined RC Columns

Structural retrofitting by wrapping with fiber reinforced-polymer (FRP) laminates can effectively increase the ductility of RC columns. The effect of the FRP-to-concrete interfacial bond on the behavior of FRP-confined RC columns has not yet been studied extensively. This paper reports on an experimental and numerical study of FRP-confined RC columns involving different bonding conditions between FRP and concrete. It was found that variations in the bonding condition do not have a significant effect on the global response of the FRP-confined RC columns. However, a detailed study of the plastic hinge zone indicated that slipping at the bond interface causes an adverse effect on the length of the plastic hinge zone. Mechanical anchoring to avoid interfacial slip can increase the plastic hinge length. The influence of the bond on the plastic hinge length was studied both analytically and numerically. Parametric studies based on finite-element analysis showed that the plastic hinge length first increases and then decreases as the amount of FRP increases, and a stronger interfacial bond offsets the decreasing trend of plastic hinge length at high FRP confinement.