Test standardisation for FRP-to-concrete bond characterisation

Brittle debonding of flexural FRP strengthening systems can occur at relatively low load levels, thus significantly reducing the FRP effectiveness and affecting the overall structural safety. Although various design models against debonding are available in the literature, they lead either unsafe or too conservative predictions. This could mainly be attributed to the lack of standardised methodology for experimental bond characterisation. Accordingly, design models continue to be developed or calibrated based on limited sets of experimental data. This paper presents an investigation into the suitability of the double shear test setup to become a standardised test and suggests potential improvements. The experimental program in this study comprised a series of 20 double shear specimens and 6 types of FRP systems. The performance of the adopted double shear test set up is analysed in terms of reliability of bond stress-slip data obtained as well as the ease of specimen preparation and testing. In addition, the influence of the roughness of the concrete substrate on bond capacity is also assessed.