Influence of Anchorage Method for Expanded FRP Strand Sheets on Anchorage Strength in Existing Concrete

Abstract

The demand for strengthening concrete structures has increased due to deterioration from aging. To address shear reinforcement, which can lead to brittle failure, an effective approach is to enhance the reinforcement by integrating non-corrosive fiber reinforced polymer (FRP) strand sheets into the concrete. This study introduces a novel reinforcement method in which FRP strand sheets are bundled, and their ends are expanded to improve anchorage performance within the concrete. We evaluated the influence of the anchoring method on the ends of the expanded FRP strand sheets through pull-out tests. The main findings are as follows: 1) The maximum load increased when utilizing resin mortar with sand, an expansion angle of 3°, and a spiral expansion method using elastic epoxy putty. 2) The anchorage length positively affected the maximum load, with increases in length leading to higher maximum loads. 3) The failure load of the FRP strand sheets with a 3° expansion correlated with the surface area of the expanded anchorage section, leading to the proposal of an empirical formula based on this relationship.