Strengthening of R/C structures under high cycle fatigue loadings

Typical strengthening systems for reinforced concrete structures are based on the use of organic matrices and carbon or glass fibers. In this book a new type of strengthening system is investigated and proposed. The system consists of high strength steel fiber tapes impregnated by a fireproof inorganic matrix. This retrofit system was used successfully to strengthen reinforced concrete beams.The results indicate that the failure of the strengthened beams was driven by yielding of the steel reinforcement in the tension face of the beams, followed by a local slippage of the steel cords from the inorganic matrix. In conclusion, the strengthening system can provide a great alternative to commercially available systems. The developed system was also investigated for the evaluation of its durability by testing R/C beams under high cycle fatigue loading bending conditions. The results show that the fatigue life of reinforced concrete beams can be significantly extended through the use of the externally bonded system. Although the fiber strengthening system increases the fatigue life of beams, the failure mechanism remains the same in both strengthened and non-strengthened beams.