Bond stress-slip behaviour of two common GFRP rebar types with pullout failure

Numerous studies on fibre reinforced plastic (FRP) rebar-concrete bond behaviour have been carried out by many researchers. However, most of the reported works have focused on the ascending part of bond-slip behaviour, especially the maximum bond stress and corresponding slip values. Fewer efforts have been made to explore the post-peak bond-slip behaviour of FRP rebars in concrete. In this study, a series of pullout tests was performed to investigate the bond stress-slip behaviour of glass fibre reinforced plastic (GFRP) bars in concrete failed by pullout under monotonic load. The test specimens were prepared using two common types of GFRP rebars (helically wrapped and sand coated) with three different concrete strengths (25, 40 and 70 MPa). The results showed quite different preand post-peak bond-slip behaviours for the two GFRP types. Based on an analysis of the experimental data from this study and additional data from a literature review, simple model equations to predict the bond stress-slip behaviour for the two GFRP rebar types are suggested. The predicted bond-slip curves showed good agreement with the test results.