Bond behaviors of pre- and post-yield deformed rebar embedded in ultra-high performance concrete

The ductility of reinforced concrete structures is often determined by the ductility of post-yield deformed rebar. However, to date, few studies have been conducted on the bond behavior of post-yield deformed rebars embedded in ultra-high performance concrete (UHPC). Therefore, a pull-out test was conducted to investigate the effects of the cover, embedded length, and steel fiber on the bond behaviors between UHPC, and pre- and post-yield deformed rebars. The test results showed that a 50% increase in the bond strength could be obtained when the cover was increased from 1d to 2d, where d is the diameter of the deformed rebar. As the anchorage length was increased from 2.5d to 5d, the bond strength decreased by approximately 50%. Meanwhile, the bond strength increased by 126% with an increase in steel fiber content from 0 to 2%. To predict the bond strength of the pre- and post-yield deformed rebar embedded in UHPC, a modified thick-walled cylinder model was proposed. Subsequently, the distribution of the bond stress along the embedded length was revealed, and the position function was provided. Finally, the bond stress–slip model including the anchorage position function provides an insight into the bond stress between UHPC and deformed rebars.