Evaluation of bond-slip behavior of reinforcement in ultra-high-performance fiber-reinforced concrete

Bond strength of steel reinforcement embedded in ultra-high-performance fiber-reinforced concrete (UHPFRC) plays a vital role in the post-cracking behavior of reinforced UHPFRC members in flexure or tension. This paper presents an analytical study on the bond strength of steel reinforcement in UHPFRC. Three different bond-slip models, namely the modified fib model, Marchand model and the proposed model are compared in the analytical method and explicit equations are also proposed. Comparisons with test data suggest that the proposed model and explicit equations can evaluate the bond-slip behavior of reinforcement with good accuracy. Marchand model shows similar predictions of bond-slip behavior to the proposed model at different load levels, whereas the modified fib model is accurate only when the reinforcement nearly yields in tension. The embedment length required for embedded reinforcement to develop its yield and ultimate strengths can also be calculated from the analytical method and explicit equations.