Design guidelines for preventing cover delamination failure

ABSTRACT

R/C beams reinforced with surface mounted fiber reinforced plastic (FRP) can fail prematurely by cover delamination due to separation of the concrete cover beneath the bottom layer of steel reinforcement. Most existing models predict cover delamination failure mode based on stress concentrations that are dependent of the properties of the bond layer. The effect of bond layer properties on cover delamination was studied based on an experimental program. The experimental results demonstrate that bond layer properties do not significantly affect cover delamination. A new model that is independent of bond layer properties is proposed and provides a correlation coefficient of 0.96 with all data available in the literature, including ACI 440 Committee’s Bond Group database for R/C beams failed by cover delamination. The model predicts loss of structural integrity in the concrete cover in a manner similar to the ACI detailed shear equation and is essentially a shear/moment interaction equation. In addition, the correlation to the failure load was further improved by including the ratio of stiffness of FRP to the

stiffness of the steel reinforcement but didn’t improve when the stiffness of FRP alone was used. This paper presents a power-law equation and design guidelines for preventing FRP cover delamination failure.