Flexural behavior of pre-damaged RC beams strengthened with UHPFRC-CFRP grid layer

Abstract

Ultra-high performance fiber reinforced concrete (UHPFRC) using recycled tyre fibers and carbon fiber-reinforced polymer (CFRP) grid were combined to strengthen the pre-damaged reinforced concrete (RC) beams caused by coupling action of sustained loads and marine environment. The flexural tests were conducted to investigate failure modes, characteristic loads, deflection features, and strain behavior of the strengthened RC beams with different configurations. The results showed that they exhibited the typical bending failure without interfacial debonding, and their cracking, yield, and ultimate loads increased by 64.7 %−152.9 %, 105.7 % to 192 %, and 65.4–131.2 % compared with that of the RC beam (B0). By increasing the thickness of the UHPFRC layer and adopting the Y-type UHPFRC (using recycled tyre fibers), the stiffness, ductility, and synergistic performance among the main materials would be further improved, while the increase of the CFRP grid layers would decrease the ductility. Furthermore, analytical models considering the coupling action of sustained loads and marine environment were developed to calculate the characteristic loads, manifesting reasonable accuracy. The proposed UHPFRC-CFRP grid strengthening method has excellent mechanical and durability performance, cost-effectiveness, and environmental benefits, which can serve as a valuable reference for the innovation and development of structural strengthening technology.