Description
The ductility and rotation capacity of steel rebar-reinforced concrete structures is one of the main advantages of this material combination. However new material combinations are arriving due to environmental issues. This can be caused by aggressive environmental conditions with an impact on the durability but on the other hand also by the demand for a reduction of greenhouse gasses. By simply replacing the steel with GFRP (Glass Fibre Reinforced Polymers) rebars a number of problems can be tackled, due to its high corrosion resistance and more environmentally friendly production techniques. However, a number of challenges should be answered in a scientifically sound way, and the redistribution capacity is one of the most important ones. Indeed, in a number of design rules of the actual codes, there is an implicit (to neglect thermal, settlements, shrink and creep effects) and explicit (for redistribution purposes) consideration of ductility, which is in general, delivered by the elastoplastic behaviour of the steel reinforcement. Facing the stress-strain relation of GFRP-rebars this desired behaviour is unfortunately lacking as the material react purely linear elastic until failure. Nevertheless, the system behaviour is not only expressed by the behaviour of concrete and the GFRP-rebar but also by the bound between the GFRP-rebar and the concrete matrix. It is already proven that here some slip can appear and this can facilitate a more ductile behaviour providing the desired ductility and rotation capacity. An experimental test set-up was built at KU Leuven Campus De Nayer consisting of two identical double span (2×1.3 m) beams (0.24×0.30 m²) and with two different configurations of upper reinforcement (so 4 beams in total). The slip of the upper and bottom reinforcement was measured together with the applied loads and observed deformations. In that way the redistribution capacity could be determined, showing the system’s ductility despite the two main brittle components. Results will be used in the framework of the revision activities of the new upcoming fib40 publication handling FRP-reinforced concrete structures.
