Loading effect on flexural strength of reinforced concrete beams before bonding externally with Carbon Fiber Reinforced Polymers (CFRP) Laminates

Abstract

The main aim of this paper is to evaluate the behaviour of RC beams strengthened with CFRP after a specified loading period. 11 RC beams were tested. One is control beam and the rest of beams were loaded statically at site using two points loading with 0 %, 25 %, 37.5 %, and 50 % of the ultimate predicted failure load for a period of 60 days. No maintenance or repair was carried out on the beams during loading period. The main variables investigated were the internal steel reinforcement ratio, and CFRP external reinforcement ratio. The beams were provided with adequate shear reinforcement with high shear capacity resistance to avoid any failure due to shear. The beams were then strengthened externally with CFRP laminates, later on they were tested to failure in laboratory. The load and deflection at midspan were recorded up to complete failure. The flexural response of the strengthened beams was investigated based on the ultimate failure load of strengthened loaded beams compared to the ultimate failure load of strengthened unloaded beams. Results show that the sustained load levels before strengthening with CFRP have no significant effect on the ultimate load carrying capacity of strengthened beams.