Exploring the Effect of Varying Fiber Dosages as Stirrup Substitutes in Torsion-Loaded Concrete Beams

Over the past few decades, numerous studies have explored the use of steel fiber (SF) as an alternative to transverse reinforcement rebars in reinforced concrete beams, either partially or completely replacing them. However, there are limited studies that have investigated the effect of fiber dosage and length on reinforced concrete beam performance under torsional loads without the use of transverse reinforcement rebars. In this study, experimental investigations were conducted to examine the performance of reinforced SF concrete beams subjected to torsional load, utilizing SFs as a complete substitution of transverse reinforcement rebars. Ten different concrete mixes with varying dosages of SFs, namely 0%, 0.5%, 1.0%, and 1.5%, were examined while maintaining the same aspect ratio for fiber length and diameter. The results revealed that the addition of SFs in the concrete mix had an impact on its properties, reducing workability but increasing flexural, tensile, and compressive strengths. By incorporating 1.0% of SFs in the concrete mix, the missing torsional strength resulting from the absence of stirrups was adequately compensated. Moreover, the presence of SFs significantly influenced the ductile behavior beyond the point of cracking in the tested beams. Hence, it is recommended that SFs are incorporated with dosages of 1.0% and 1.5% in the concrete mixture, particularly for beams subjected to torsion, as a viable substitute for stirrups.