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 pro-posed. Subsequently, the distribution of the bond stress along the embedded length was revealed, and the po-sition 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.