Prediction of Shear Capacity of Slender Reinforced Concrete Beams with Steel Fiber

Abstract

The objective of this research is to propose a simple and accurate prediction method for the shear capacity of reinforced concrete beams with steel fiber (RSF beams). Steel fiber reinforced concrete (SFRC) is being widely used nowadays, with the steel fibers added to the concrete to improve the tensile resistance. First, this research aims to investigate the material properties of SFRC in various concrete compressive strengths, shapes of steel fiber and volume fractions of steel fiber. In order to evaluate the shear capacity, several material properties, such as tension softening curves and fracture energy were investigated in the material tests. Second, four-point bending tests of RSF beams were conducted in order to investigate the shear capacity and diagonal crack pattern. Eight RSF beams with various concrete compressive strengths, volume fractions of steel fiber and stirrup ratios were fabricated and tested. The results revealed that the concrete compressive strength and steel fiber significantly affect the shear capacity of RSF beams. Finally, the shear equation for the RSF beams failing in a diagonal tension failure mode has been proposed by focusing on the residual tensile stress perpendicular to the critical diagonal crack at the failure condition.

Shear Design of Strain-Hardening Fiber-Reinforced Concrete Beams

“…Reinforced with a high dosage of discontinuous steel fibers, typical UHPC-class materials exhibit tensile strength exceeding 7.0 MPa (1.0 ksi) sustained well into the postcracking stress-strain regime. This behavior is shown to contribute significantly to the shear capacity of beams because fibers transmit forces across diagonal cracks, thus supplementing or even replacing the transverse reinforcement in resisting shear forces (Voo et al 2006;Voo and Foster 2008;Baby 2012;Kamal et al 2014;Pourbaba et al 2018;El-Helou and Graybeal 2019;Hemstapat et al 2020). Recent experimental investigations on UHPC beams and panel elements showed that, given the high compressive strength of UHPC, the shear failure is often controlled by the tensile behavior rather than compressive failure (Voo et al 2010;Baby et al 2014;Ahmad et al 2019;Yap 2020;El-Helou and Graybeal 2022b).…”