This paper investigates the bond behaviour of lapped steel bars using fifteen RC beams tested in flexure. Twelve of the beams were designed to fail by bond splitting at midspan, where the main flexural reinforcement was lapped 10 bar diameters. The parameters studied include the amount and type of confinement at midspan (no confinement, internal steel stirrups or externally bonded carbon FRP), concrete cover and bar size. The results show that the CFRP confinement enhanced the bond strength of the lapped bars by up to 49 % with reference to unconfined beams, and improved significantly the overall behaviour of the specimens. The experimental results are compared with existing models to predict the bond strength enhancement provided by CFRP confinement. It is shown that existing models overestimate considerably the CFRP strains and show a large scatter when predicting experimental results. Based on the test results, a new approach to predict the bond strength enhancement due to CFRP confinement is proposed. This can be used during the assessment and strengthening of substandard RC constructions. © 2013 RILEM.
Journal / conference name:
Materials and Structures/Materiaux et Constructions