Shear behavior of prestressed UHPC rectangular beams: experimental investigation and limit equilibrium state-based prediction method.

Ultra-high performance concrete (UHPC) is a durable and versatile construction material that enables the engineering of slender fabricated beams. Nonetheless, existing design methodologies exhibit certain discrepancies in predicting the ultimate shear capacity of UHPC beams. This study aimed to develop an improved predictive shear model based on design and mechanical properties. Eleven prestressed rectangular UHPC beams were subjected to shear tests, systematically investigating essential design parameters such as shear-span-to-depth ratio, stirrups ratio, longitudinal reinforcement ratio, prestressing force, and prestressing type. The results demonstrated that UHPC beams exhibit strain-hardening behavior after cracking, accompanied by the formation of dense diagonal cracks. Localized cracking eventually led to shear failure. The shear behavior was primarily influenced by the shear-span-to-depth ratio, showing an inverse relationship with shear strength. Increasing the longitudinal reinforcement ratio, stirrups ratio, and prestressing force marginally improved shear capacity. Furthermore, a limit equilibrium state-based method was proposed to develop a practical prediction formula that incorporates steel fibers and matrix interaction. The proposed method demonstrated superior accuracy compared to existing design models, displaying an average difference of 1.1% and a correlation coefficient of 0.96 with experimental results. [ABSTRACT FROM AUTHOR]