Effect of Circumferentially Nonuniform Lateral Tension on Bond Behavior between Plain Round Bars and Concrete: Analytical Study

The bond behavior between a plain bar and concrete has received more attention in recent years because of its importance in the assessment of historical structures. The negative effect of lateral tension on the bond performance of plain bars has been previously investigated through experiments, and the results have shown that the bond strength decreases with increases of lateral tension. However, few attempts have been made to analytically study the bond behavior of plain bars under circumferentially nonuniform lateral tension. Therefore, in this study, a theoretical investigation into the effect of circumferentially nonuniform lateral tension on the bond mechanism and ultimate bond strength of plain bars is undertaken. Based on the theory of elasticity, the compaction of the bar/concrete bond interface is first discussed, and then an analytical model is given for the ultimate bond strength of plain round bars under circumferentially nonuniform lateral tension. The proposed model is verified with experimental results from 96 pull-out specimens, which agree well with the test data. Furthermore, a parametric study is made to show that the proposed model can be applied without concern for separation of the bar/concrete interface for most historical RC structures except those located in humid or marine environments. Finally, the analytical results are compared with a design bond-strength code, which shows that the code could be used in calculating the development length of plain bars under lateral tension.