Bond properties of deformed steel bars in concrete during construction under reversed cyclic loading

Abstract

To investigate the bond properties of deformed steel bars in concrete during construction under reversed cyclic loading, concentric pull-out tests under reversed cyclic loading were performed on specimens with six concrete ages and three concrete strength grades. The effects of concrete age and strength grade on the following bond response indicators were examined: maximum bond stress, slip corresponding to the maximum bond stress, residual bond stress, cumulative energy dissipation, unloading stiffness, and frictional bond stress factor. The results indicated that for specimens with the same concrete strength grade, with an increase in the concrete age, the maximum bond stress, residual bond stress, unloading stiffness, frictional bond stress factor, and energy-dissipation capacity increased, whereas the slip at the maximum bond stress decreased. Moreover, with regard to specimens with the same concrete age, with increasing concrete strength grade, the maximum bond stress, residual bond stress, unloading stiffness, frictional bond stress, and energy-dissipation capacity increased, whereas the slip corresponding to the maximum bond stress decreased. According to the analysis of the bond properties of the specimens with different concrete ages and strength grades, empirical bond stress–slip models of a deformed steel bars in concrete during construction under reversed cyclic loading were proposed. A good agreement was observed by comparing the proposed models with the experimental results in this study and the existing models in the literature.