External strengthening of shear deficient reinforced concrete beams with flexural CFRP laminates

Abstract

This paper presents an experimental investigation of reinforced concrete (RC) beams strengthened in shear with externally bonded flexural carbon-fiber reinforced polymer (CFRP) sheets attached to the soffit of the beam via epoxy adhesives. The current state-of-the-art technology of shear strengthening of RC beams is by externally bonding CFRP sheets or plates to the vertical sides of the beam’s web with different orientations and configurations using epoxy adhesives. However, in certain applications, the sides of the beam might not be accessible for shear strengthening or might be too shallow to develop the strength of the CFRP laminates without anchors. Therefore, the objective of this study is to investigate the contribution of external flexural longitudinal CFRP laminates on the shear strength of RC beams casted without internal stirrups. The beam specimens were simply supported and tested under four point bending and the load versus mid-span displacement responses were recorded until failure. As expected, all beams failed in shear as a result of a diagonal-tension crack. The strengthened specimens showed an increase in the load-carrying capacity of 49%-61% over the control unstrengthened specimen. It could be concluded that external flexural CFRP reinforcement has a significant effect on the concrete shear strength of beams and could be used as a valid alternative when the vertical sides of RC beams are not accessible.