Experimental Study on Flexural Behavior of Retard-Bonded Prestressed UHPC Beams with Different Reinforcement Ratios

Ultra-high performance concrete (UHPC), functioning as a next-generation cementitious engineering material, demonstrates marked superiority over conventional concrete in critical performance metrics, with its groundbreaking characteristics primarily manifested through exceptional strength and enhanced durability parameters. To address structural demands for reduced self-weight, material efficiency, and simplified construction processes in large-span durable structures, this study proposes a retard-bonded prestressed UHPC (RBPU) beam combining UHPC with retard-bonded prestressing tendons (RBPTs). Three RBPU beam specimens, with varying reinforcement ratios, underwent flexural testing to quantitatively assess their bending performance characteristics, providing foundational references for design optimization. The test results show that the failure mode of RBPU beams is typical flexural failure, demonstrating good load-bearing capacity and excellent ductility. As the reinforcement ratio increases, the cracking moment (M_cr) is improved to some extent, while the ultimate moment (M_u) and ductility are significantly enhanced. The plastic influence coefficient of the section modulus (γ) in the calculation of the M_cr was revised, and the ultimate moment M_u was subsequently calculated. The comparison demonstrates good agreement between the experimental values and computational results. This study provides both experimental and theoretical references for further in-depth research and practical applications of RBPU beams.