Shear transfer model for ultra‐high‐performance concrete incorporating fiber bridging mechanism

Abstract Ultra‐high‐performance concrete (UHPC) exhibits exceptional mechanical properties, including high shear strength, partly attributed to the fiber bridging mechanism. However, existing shear transfer models for normal‐strength concrete have not considered the significant contribution of fibers. This study proposes a refined shear transfer model for UHPC that explicitly incorporates the fiber bridging mechanism. The model was developed based on experimental data and digital image correlation (DIC) analyses to accurately capture the stress–strain behavior of UHPC under monotonic and cyclic shear loading, ranging from infinitesimal to localized large deformations under different confinement conditions. Reasonable correlations were found in the analyses of experimental stress–strain behavior. Accordingly, the model was proposed to incorporate the effect of compressive strength, bond stress between fiber and UHPC, crack slip and opening, fiber orientation, fiber volume fraction, and fiber aspect ratio. Notably, the contact density model originally developed for normal‐strength concrete was applied to the shear transfer model of UHPC, which has additional functions for the fiber bridging mechanism and confinement effect. According to the model, it was identified that the fiber bridging mechanism provides approximately one‐third of the total shear capacity of UHPC.