1 School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China 2 China Communications No.1 Aviation Bureau Company, Tianjin 300000, China
Abstract: At present, the strength of steel bars studied and applied in China is still lower than that in western developed countries. At the same time, there is a common problem that the strength of steel bars increases but the ductility decreases. Therefore, the research and development of new high strength and high ductility steel bars is an effective way to solve the problem of building steel in China. In order to explore whether the NPR steel bars can be applied to concrete structure, this paper studies the bond performance between the NPR steel bar and marine concrete by central pull-out test. In this paper, the failure mode of the specimens was observed, and the influence of reinforcement type (NPR steel bars, ordinary steel bars), strength grade of marine concrete(C30F250, C40F250, C50F250), diameter of steel bars (8 mm, 18 mm) and bond length (5d, 7d) on bond strength and bond stress-slip curve was analyzed. The results show that the type of reinforcement has a significant influence on the failure mode, bond strength and bond stress-slip curve. When other conditions are the same, the bond strength of NPR steel bar is lower than that of ordinary steel bar, and the bond strength of NPR reinforcement increases with the decrease of bond length and the improvement of strength grade of marine concrete. Meanwhile, the three-stage bond slip constitutive model is used to fit the bond stress-slip curve. The results show that the three-stagment model can better describe the characteristics of the bond stress-slip curve of NPR steel bar and marine concrete.