Enhancement of bond characteristics between sand-coated GFRP bar and normal weight and light-weight concrete using an innovative anchor

To prevent the concrete bar from slipping, a common approach is to ensure an adequate development length or bend it upwards. However, in the case of fiber reinforcement polymer (FRP) bars, on-site bending is not feasible. Therefore, employing a mechanical end-anchor offers an alternative solution to enhance the bond in reinforced concrete. This study investigates the influence of end-anchor shape on ribbed sand-coated glass fiber-reinforced polymer (GFRP) bars, utilizing four different types of mechanical end-anchors. Additionally, the effects of concrete type and compressive strength are evaluated by considering normal-weight concrete (NC) and light-weight concrete (LC) with compressive strengths ranging from 26 MPa to 38 MPa. The study involves the preparation and testing of 60 specimens using a direct pull-out test. The findings demonstrate that the utilization of the proposed mechanical end-anchors enhances the developed tensile stress of the GFRP bar by 10% to 50%, consequently significantly increasing the ultimate capacity of the reinforced concrete section. Furthermore, optimizing stress distribution and improving the bond behavior between the bar and concrete can be achieved by increasing the number of end-anchors and adjusting the distance between them, while maintaining the total length and diameter.