Pullout strength models for FRP anchors in uncracked concrete

Mechanical anchorage can delay or even prevent premature debonding failure in externally bonded fiber-reinforced polymer (FRP) composite strengthening systems. A promising type of anchor made from FRP, which is known as a FRP spike anchor or FRP anchor among other names, is noncorrosive and can be applied to a wide range of structural elements and externally bonded FRP strengthening schemes. Experimental investigations have shown FRP anchors to be effective under tension (pullout) and shear loading, however, few analytical models exist to date. This paper in turn presents analytical models to quantify the pullout strength of FRP anchors. As existing research on the pullout behavior of metallic anchors is partially relevant to FRP anchors, this paper first presents a review of current pullout strength models for metallic anchors. These models are then assessed with experimental data of FRP anchors and modified and recalibrated where appropriate. As a result, simple and rational pullout strength models for FRP anchors are proposed which can also be used in design. Finally, parametric studies are undertaken and the influence of key variables is identified.