Theoretical and experimental assessment of the effect of adhesive bond thickness on the flexural capacity of CFRP strengthened beams

Abstract

Carbon Fiber Reinforced Polymer (CFRP) is a material of choice in the structural strengthening of reinforced concrete (RC) elements. In order to strengthen RC elements, CRFP is bonded externally to RC elements using adhesives.  This paper investigates the effect of varying adhesive bond thickness on the moment capacity of CFRP strengthened RC beams in flexure. Thirty-eight (38) Reinforced concrete beams (1.2m length) were cast in the laboratory and their failure loads and corresponding moment capacities obtained when the adhesive bond thickness between the CFRP wraps and RC beams were varied. This paper examines the comparison between flexural moment capacities obtained experimentally and the predicted moment capacities using a theoretical procedure set out in AC440-2R-17 after structural strengthening with CFRP. It was observed that the adhesive thickness had a significant effect on the flexural capacity of strengthened beams. As the adhesive thickness increased beyond certain thresholds, the flexural capacity of strengthened beams reduced. At the optimum adhesive thickness threshold, the ACI 440-2r-17 procedures could predict to high accuracy the moment capacities of strengthened beams.