Shear behavior of ultra-high-performance concrete (UHPC) beams that replace the stirrups with externally web-bonded steel plates

This study proposed a novel ultra-high-performance concrete (UHPC) beam that replaces the stirrups with externally web-bonded steel plates (UB-WSPs) to enhance construction efficiency and structural performance. Seven specimens, including five UB-WSPs and two UHPC beams with/without stirrups, were designed and tested to investigate the shear behavior of UB-WSPs. The effects of different parameters (including cross-sectional area, spacing, and inclination of steel plates) on the ultimate capacity, ductility, and failure modes were explored. The results indicate that UB-WSPs and UHPC beams with stirrups exhibited a shear capacity improvement ranging from 12.6 % to 46.4 % in comparison to UHPC beams without stirrups. While UBs-WSPs exhibited slightly lower shear capacity than UHPC beams with stirrups, they showed better ductility. Diagonal cracks intersected the WSPs, which functioned similarly to stirrups in providing shear resistance. Specimens with inclined WSPs showed equivalent shear capacity to those with vertical WSPs but exhibited a more gradual descending branch in their load-deflection curves. Additionally, the shear contribution of shear resistance components was analyzed to explore the shear mechanism of UB-WSPs. The shear contribution of WSPs to the beam was nearly double that of the stirrups to the beam. Based on the truss-arch model, a method for calculating the shear strength of UBs-WSPs was proposed and validated against the test results. These findings demonstrated the feasibility and advantages of UBs-WSPs in practical application. The UB-WSPs can improve the ductility of no-stirrup UHPC beams and simplify the construction process compared to UHPC beams with stirrups.