Structural behaviour of CFRP reinforced concrete members under monotonic and cyclic long-term loading

A large percentage of the damages to reinforced concrete structures is caused by corrosion of the reinforcement steel, which often leads to expensive repairs or new construction of existing structures. Due to their high strength and resistance to corrosion, reinforcements made of carbon fibre-reinforced polymers (CFRP) are becoming more and more important in structural engineering. It is expected, that the service life of CFRP reinforced concrete (RC) members can be significantly increased as the strength-reduction due to corrosion is negligible compared to conventional RC members. Therefore, precise knowledge of the long-term behaviour of CFRP RC members is required in order to ensure safe and economic design. This paper presents experimental investigations on the long-term behaviour of CFRP RC members as well as steel-reinforced RC members under monotonic and cyclic long-term loading with varying load levels, different cross-sectional shapes and shear slendernesses. Accompanying experiments on the concrete creep behaviour that were conducted within the investigations are shown. Within the scope of the experiments, the deflections as well as the strains on the top and bottom side of the RC members were measured using displacement sensors and strain gauges. The experimental data is evaluated, especially with regard to the time-dependent deflections. The data is compared to existing mechanical and empirical models, which are usually derived for steel-reinforced RC members. Based on the experimental data, the time-dependent reduction of stiffness and conclusions for the calculation of deflections are shown.