Post-yield bond behavior of reinforcing bars embedded in concrete under axial loading up to fracture

Deformation capacity of Reinforced Concrete (RC) structures is very critical to resist progressive collapse. Previous research has indicated that for framed RC structures both flexural rotation and fixed-end rotation of beams are the main contributions to the structure deformation, in which the latter is mainly attributed to the slip of bars embedded in concrete, such as at beam-column joints. In modern RC structures, reinforcing bars are typically continuous in interior joints. Therefore, an experimental program was conducted to investigate the slip and bond stress of the bars embedded in concrete under axial loading up to bar fracture, in particular, the post-yield bond stress. To this end, bars were smoothly grooved along the longitudinal ribs, and a series of strain gages were attached in the grooves before casting concrete. In this paper, the experimental results of three specimens with the same bar diameter but different geometric configurations were presented in terms of bar strain, slip and bond stress distribution along an entire bar. Also, the average bond strength at elastic and plastic part of a bar was evaluated.