Shear behavior of externally prestressed UHPC beams without stirrups

Abstract

Shear stirrups in a prestressed ultra-high performance concrete (UHPC) beam might be eliminated due to the high tensile strength of UHPC. This research aims to investigate shear behavior of the externally prestressed UHPC beams without stirrups. Thirteen UHPC beams were tested with the experimental parameters of prestressing level, shear span-to-depth ratio, longitudinal reinforcement ratio, fiber content, and stirrup ratio. The results showed that the beam with the longitudinal reinforcement ratio of 2.0 % under a shear span-to-depth ratio of 2.0 failed in flexure, even though additionally applying a higher prestressing up to 40 % of tensile strength of prestressing tendon. However, the externally prestressed UHPC beams under a shear span-to-depth ratio lower than 2.0 failed in shear. The shear strength of UHPC beam increased with a higher prestressing, lower shear span-to-depth ratio, more longitudinal reinforcements and stirrups, and higher fiber content. French Standard formula and PCI formula for shear design were conservative, irrespective of the existence or absence of stirrups in the prestressed UHPC beam. The calculated results indicated that the externally prestressed UHPC beams met the requirement of shear design codes when no stirrup was employed.