Modelling the ultimate shear behaviour of UHPFRC deep beams

Abstract

Due to the ability of deep beams to transfer loads by direct strut action, they are often used to resist large shear forces. In the past decade, researchers have studied the use of ultra-high-performance fiber-reinforced-concrete (UHPFRC) in deep beams due to its enhanced mechanical and durability properties compared to other materials (i.e., reinforced concrete and fiber-reinforced-concrete). However, there is still a need for adequate mechanical models to predict the shear strength of UHPFRC deep beams in a simple and rational manner. To address this gap, the current study proposes a kinematic-based model incorporating structural fundamentals: compatibility of deformations, constitutive relationships, and equilibrium. The proposed model stems from a kinematic-based model developed for the ultimate shear behaviour of FRC deep beams, and it accounts for the enhanced mechanical properties of UHPFRC. The model is validated using 23 tests featuring a wide range of properties. The model adequately predicts the shear strength with an average experimental-to-predicted ratio of 1.07 and a coefficient of variation of 14.7%. Additionally, the effect of the main test variables on the shear strength is also found to be well captured in demonstration of the reliability of the proposed model.