Experimental and Analytical Investigation of Hybrid Layer Thickness Effect on Replacing the Rebar for Reinforced Concrete Beams

Abstract

Many researchers emphasize the effectiveness of steel fiber to replace the reinforcing bar in the reinforced concrete structural elements. The fiber of different types, sizes and geometries have been added to the concrete mix with a pozzolanic material to produce Ultra-High Strength Concrete (UHSC), which has excellent properties, high strength, and durability. This paper is a lab work and theoretical study consisting of casting and testing. Twenty-one simply supported RC beams to examine the beam's behavior and the shear capacity with the full or partial depth of UHSC with or without steel fibers (UHSSFRC) for replacing the reinforcing bars. The beams were divided into five groups. Preliminary experiments tests were conducted and carried out to study hardened properties of concrete such as (compressive strength, splitting tensile strength, modulus of rupture and modulus of elasticity). The selected finite element program (ANSYS) was applied to model all tested beams. It was observed that the performance of the finite element representation gives and shows good agreement with the lab work results. The test consists of failure load, deflection, cracks and failure mode. The experimental laboratory work results showed that for (1% steel fiber with reinforcement ratio ρ=0.0105 full UHSC layer) was able to give the same shear capacity for beam with (reinforcement ratio ρ=0.0157 regular concrete), while for (2% steel fiber half UHSC layer and reinforcement ratio ρ=0.0105) was able to give the same ultimate shear loads of beam with (reinforcement ratio ρ=0.0157 normal concrete). This research reveals that the hybrid layer and steel fiber effects were able to substitute for a higher reinforcement ratio with the same shear capacity.