ROUND ROBIN TEST ON THE BOND BEHAVIOUR OF EXTERNALLY BONDED FRP SYSTEMS TO CONCRETE

The performance of an externally bonded FRP strengthening system is often limited by its ability to effectively transfer stresses between the FRP reinforcement and the concrete substrate. As evidenced in the literature, debonding of the FRP reinforcement can occur at a level of strain well below its ultimate strain limit and generally results in a brittle type of failure. An accurate characterisation of the bond behaviour between an FRP system and concrete is therefore critical for the optimal design and detailing of a strengthening solution. Although various test methods to examine the local bond behaviour of externally bonded FRP systems have been proposed thus far, their implementation can lead to a wide range of results and a standard methodology has yet to be generally accepted. With these issues in mind, a Round Robin Testing (RRT) programme was carried out to assess the performance and reliability of small scale testing on various externally bonded FRP strengthening systems. Seven laboratories and four manufacturers and suppliers participated in this extensive international exercise, which was initiated within the framework of the European funded Marie Curie Research Training Network, EN-CORE, with the support of Task Group 9.3 of the International Federation for Structural Concrete (fib). This paper describes the proposed testing programme and summarizes the results obtained by the participating laboratories. The influence of various parameters on the bond behaviour of the examined strengthening systems is discussed and recommendations on testing procedures are given.