Bond clause proposal for FRP-bars/rods in concrete based on CEB/FIP Model Code 90 with discussion of needed tests
The bond clauses in the CEB/FIP Model Code 1990, (MC90), were written for steel reinforcement in concrete. After finalization of the MC90 the further work within CEB and after the merger with FIP in the new organization fib should be directed towards covering up lacunae and also adapting the Model Code to new materials. The basic MC90 concepts should be kept when applied to new materials. Models should be used to justify the clauses. However, the bond clauses in MC90 were not fully based on models, because there are very many options for bond failures and it is difficult to cover up these with few models. Reinforcing steel is more or less just one material. FRPs, on the other hand, are made of a lot of different materials with manifold shapes and all these FRPs perform differently in many contexts. Especially in severe environments, where steel is not durable, FRPs may perform well. To make use of the fiber composites, it is necessary to bring these materials to codes of practice and the closest is to try to adapt the code for steel reinforced concrete to FRP reinforced. The clauses should be given with boxed values open for individual coefficients for different FRPs. The necessary coefficients should be determined for the code models using systems of appropriate and coupled test methods.