Numerical Verification of the Use of GFRP Reinforcement in the Ceiling Slab of a Garage House

One of the major advantages of fibre reinforced polymers (FRPs) is their high tensile strength and low weight to strength ratio. Compared to steel reinforcement, this is one of the main and decisive features that could determine the choice of materials used in the design. Since there is no corrosion for this type of reinforcement, it is very suitable for concrete structures in aggressive environments. This point, along with others, gives concrete structures reinforced with FRPs significant advantages over conventional concrete structures with steel reinforcement. Different material properties and behaviour of FRP when compared to steel reinforcement result in the need of the modification of established design procedures, especially in the area of the ultimate strain, because FRP reinforcement has a different σ-ε diagram than the steel reinforcement. The experimental verification of the new design procedures is necessarily needed. This paper summarizes the results of practical design and calculations of the resistance of alternatively steel and GFRP reinforced concrete ceiling slab of a garage house and experimental results on the beam specimens reinforced with GFRP reinforcement tested under four-points test. It was necessary to adjust the conventional procedures in calculating the required area of GFRP reinforcement in order to avoid brittle failure of the cross-section (rupture of reinforcement). This is ensured by abiding the balance reinforcement level. Another fact to be considered is the creep rupture phenomenon causing immediate rupture of GFRP reinforcement under a high level of sustained loading. The reduction of GFRP strength according to the long-term loading results in rising required area of reinforcement. Finally, the serviceability limit state is checked. According to the low modulus of elasticity of GFRP reinforcement, the deflection should be the limiting factor for the amount of reinforcement designed.