Bond Behavior of Spiral Ribbed Ultra-high Strength Steel Rebar Embedded in Plain and Steel Fiber Reinforced High-Strength Concrete

The bond behavior of spiral ribbed ultra-high strength (SRUHS) steel rebar embedded in plain high strength concrete (HSC) and steel fiber reinforced high strength concrete (SFRHSC) is experimentally studied using pull-out tests. The influencing factors of concrete type, embedded length, cover thickness and stirrup ratio are considered and the bond failure characteristics as well as the whole process of stress-slip behavior are analyzed. The research shows good anchorage ductility between SRUHS steel rebar and HSC. Since SRUHS steel rebars have continuous spiral bite teeth with concrete, the concrete in the rib dales is not easily sheared off, thereby leading to a reliable bond strength. Compared to specimens without steel fibers, steel fiber reinforcement can increase the ultimate bond strength, bond stiffness and residual strength. Meanwhile, it will also reduce the influence of cover thickness, stirrup ratio on the specimens with steel fibers. Finally, a prediction calculation for ultimate bond stress and an analytical model for bond stress-slip relation are proposed, which match well with test results.