Strength and Ductility of Reinforced Concrete Beams Externally Reinforced with Carbon Fiber Fabric

Epoxy-bonding composite materials to the tension face of reinforced concrete beams is an effective technique for shear/flexural strengthening. To ensure successful and cost-effective applications, engineers must improve their knowledge with respect to the actual behavior of strengthened structures. This paper presents results obtained from an experimental investigation of reinforced concrete beams strengthened in flexure and shear using externally epoxy bonded bidirectional carbon fiber fabric. Two series of three large-scale concrete beam models were built and tested under four-point bending. The beams of the two series were internally reinforced with high-tensile steel for both shear and flexure. One beam for each series was used as a control beam without external reinforcement. The difference between the two series consisted in the amount of internal stirrups and concrete strength. To study the effect of the external composite reinforcement, variations in the number of layers applied and in the external end arrangements were made. One type of external reinforcement consisted of two layers of fabric bonded to the tension face of the beam and partly extended zip to the vertical sides. The second arrangement consisted of four layers of fabric and supplementary end anchorages. The composite reinforcement led to an increase both in the load-carrying capacity at ultimate and flexural stiffness as compared with the control beams. Significant reductions in deflection, curvature, and structural ductility were also observed.