Flexural Strengthening of Reinforced Concrete Beams with Externally Side-Bonded CFRP Laminates

A Master of Science thesis in Civil Engineering by Ahmad S. D. Salama entitled, "Flexural Strengthening of Reinforced Concrete Beams with Externally Side-Bonded CFRP Laminates," submitted in April 2016. Thesis advisor is Dr. Rami Hawileh and thesis co-advisor is Dr. Jamal A. Abdalla. Soft and hard copy available.

Abstract

Carbon fiber reinforcement polymer (CFRP) composite sheets and plates are widely used nowadays in civil engineering applications to externally strengthen structural concrete elements against deficiencies in flexure and shear. These deficiencies could be due to an increase in loading, earthquake damage, or even design and/or construction defects. The current state of the art technique used in flexural strengthening of reinforced concrete (RC) beams is the externally bonding of CFRP sheets or plates to the beam's tensile bottom surface (soffit). However, the beam's soffit may be obstructed and not always readily accessible for strengthening. Only the beam's sides that may be exposed become the only accessible area for strengthening using side-bonded CFRP sheets or plates. As a result, this study aims to evaluate the performance of RC beams externally strengthened in flexure with side-bonded CFRP composite sheets. Accordingly, a total of 25 beams has been cast and strengthened in flexure with different configurations of side-bonded CFRP sheets. The strengthening scheme, amount of steel and CFRP reinforcement were varied to examine their effect on the flexural strength and ductility of RC beams. The flexural strength and load-deflection response curves of the tested specimens were also predicted using the ACI 440.2R-08 design guidelines. The predicted results were in good agreement with the experimental results. It was concluded that the side-bonded strengthening scheme is less efficient than that of the conventional soffit-bonded one; however, it is a viable solution when the beam's soffit is not accessible for strengthening. The debonding mechanism of the side-bonded specimens justifies the efficiency reduction in this technique, since the stress distribution is not uniform along the CFRP sheets as in the soffit-bonded ones. However, as the reinforcement ratio increases, the performance of both strengthening schemes exhibit similar performance.