Bonding behavior of lap-spliced reinforcing bars embedded in ultra-high-performance concrete with steel fibers

This study explores the bond strength of steel reinforcing bars in normal concrete (NC) and ultra-high-performance concrete (UHPC) with steel fibers, focusing on the behavior of lap-spliced rebars. Key variables such as rebar diameter (D), spacing (s), lap-splice length (L 1 ), and hook length (L 2 ) were evaluated to understand their impact on bond performance. Both NC and UHPC increase in bond strength with greater spacing and lap-splice length, with UHPC demonstrating significantly stronger bond characteristics due to its higher compressive strength. A novel predictive method for calculating bond strength is proposed, offering practical guidance for designing lap-spliced rebars in construction, and includes reduction factors tailored for realistic construction settings. This method achieves an error margin below ±16.5%, providing an accurate approach for practitioners. This rational method incorporates both engineering and economic considerations, particularly valuable for applications in precast concrete structures where enhanced bond performance and durability are essential. • This research investigates the bond strength of steel rebars in NC and UHPC. • Pull-out tests is conducted on lap-splice tests with and without hooks. • Bond strength increases as the spacing, and lap-splice length increase. • A novel method for predicting the bond strength is proposed.