International qualification approaches and experimental assessment of embedded FRP reinforcement of concrete structures

Fibre reinforced polymer (FRP) bars are increasingly being used as reinforcement of concrete structures for their high durability in comparison to steel, especially in aggressive environments. The design of embedded non-metallic reinforcements has been only recently introduced in the Eurocode 2 (EN 1992-1-1), even if their application dates back to the early 90’s. The use of FRP bars is strongly influenced by their physical and mechanical properties, mainly dependent upon the characteristics of the FRP constituents (fibres and organic matrixes), but also by loading history, temperature, humidity. Therefore, for a proper design of FRP reinforced structures, the correct assessment of the composite material properties becomes a key factor. The works for a comprehensive document which could include the essential characteristics of the bars and stirrups and their assessment methods have been recently completed at the European level. The document introduces tests for the main mechanical (tensile, compressive and shear) and physical (glass transition temperature, coefficients of thermal expansion, etc.) properties, but also interaction with concrete elements, behaviour under various exposure and loading conditions. The paper will present the assessment methods there introduced for the qualification and CE marking of FRP bars, strictly connected to the design included in the current Eurocode 2. To evidence the influence of assessment methods on different types of non-metallic reinforcing bars, the experimental results of specific tests on a few commercial glass FRP products will also be presented and analysed.