Integration of CFRP strips as an internal shear reinforcement in reinforced concrete beams

Carbon fiber reinforced polymer (CFRP) composites have wide applications as an external strengthening/repair technique for deteriorated reinforced concrete members. Nevertheless, debonding and anchoring problems remain a challenge for success of this technique. In this study, an innovative application was implemented in which CFRP strips were integrated as internal shear reinforcement for reinforced concrete beams. The intent was to assess the contribution of the CFRP strips to the shear strength and thus evaluating the effectiveness of using them as main or supplemental shear reinforcement. Internal application of CFRP strips does not require an epoxy for attaching them, as they can be cut without difficulty to any width/length and then attaching them to the main steel bars. Similar to the steel shear stirrups, the CFRP strips work integrally with the beam concrete and steel reinforcement as they are confined by the concrete. The investigated parameters include the area and number of layers of CFRP strips. Through demonstrating an outstanding structural performance with significant enhancement in the ultimate strength, ultimate deflection, stiffness, and toughness, the findings of this paper strongly attest that CFRP strips can be effectively utilized as an internal shear reinforcement in reinforced concrete beams. Using just 5 cm CFRP strip (one on each side) enhanced the ultimate shear strength of the beam by 30%; the shear capacity was nearly doubled when the shear span was fully strengthened with CFRP strips.