Effect of bond surface area on the shear strength of carbon fibre reinforced polymer (CFRP) strengthened reinforced concrete beams

Abstract

The use of carbon fiber reinforced polymer (CFRP) for shear strengthening of reinforced concrete (RC) elements has grown significantly over the last few decades. The effectiveness of a CFRP strengthened system depends primarily on the bond strength between the CFRP and RC substrate. Since cost of CFRP and bond materials (epoxy adhesive) is relatively high, it is important to reduce CFRP bond surface area to RC when carrying out structural strengthening. This paper reports the effect of bond surface area on the shear strength of RC beams externally bonded with CFRP. Seven RC beams were investigated. One of the beam specimens was not strengthened and was used as a reference. The remaining six beams were strengthened with 200 g/m2 and 300 g/m2 CFRP fabrics with three different bond surface areas, i.e., 0.15 m2, 0.2 m2 and 0.25 m2 in a U-wrap configuration. Static bending tests were performed on all the beams. Results show that the CFRP's contribution to shear strength increases as the bond surface area increases. Results also show that the shear strength of the RC beam was increased by 45% due to the presence of CFRP. Fundamentally, this work presents a parametric study to guide engineers on how shear strength and corresponding ductility of beams can be increased with an optimal configuration of the bond surface between CFRP and RC elements. An optimal and cost-effective configuration is proposed for carrying out nominal shear strengthening of RC elements after construction, especially in cases where the construction engineer has concerns about the shear stirrups provided before casting.