A mechanical bond model for reinforcing bar in concrete subjected to monotonic and reversed cyclic loading

The reinforcing bar with diameters of 10 mm and 12 mm are widely used in shear walls, whose bond-slip performance has great influence on the seismic performance of the shear walls. Besides, the bond stress-slip model plays an important role in the theoretical analysis of the seismic performance of shear walls. Therefore, an analytical solution for the maximum bond stress was carried out and modified based on the thick-walled cylinder model and the tensile stress-strain model of concrete. The bond-slip tests of reinforcing bars in concrete were conducted on 48 specimens under monotonic and reversed cyclic loading. The effects of concrete strength, diameter of bar and bonding length on the bond-slip performance were examined and analyzed. The test results showed both the maximum bond stress and residual bond stress increased with increasing concrete strength, but decreased with increasing diameter of bar or bonding length. The reversed cyclic loading can cause the degeneration of the maximum bond stress and the bond stiffness. According to the bond-slip performance, the bond stress-slip model was established based on the analytical solution for the maximum bond stress, which is suitable for calculating both monotonic and reversed cyclic loading. A good agreement was observed by comparing the proposed models with the test curves in the study.