Abstract
This study investigates the possibility of replacing the minimum web reinforcement in deep beams with discrete fibers. Additionally, the equivalent dosage of fibers required to obtain similar performance of the deep beam with minimum web reinforcement is investigated. Deep beams made of plain concrete with no fibers, beams with minimum web reinforcement as per AASHTO LFRD recommendations (0.3% in both horizontal and vertical), and with a 0.5% volume fraction of steel, macro-synthetic and hybrid fibers are tested at a shear span to height ratio (a/h) of one. Test results show that the presence of 0.3% web reinforcement in horizontal and vertical directions increased the peak load by 25% compared to the plain concrete beams. However, it did not significantly change the first diagonal crack load. With the addition of 0.5% of steel, macro-synthetic and hybrid fibers, the peak load increased by 49%, 42%, and 63%, respectively, compared to the plain concrete specimen. The addition of steel fibers significantly improved the first cracking load. In contrast, macro-synthetic fibers did not affect the first cracking load but improved the ductility with higher deflections at peak. Hybridization of steel and macro synthetic fibers showed improved performance compared to the individual fibers of the same volume in peak load and ductility. Test results showed that a 0.5% volume fraction of discrete macro steel or synthetic or hybrid fibers can be used to completely replace the minimum web reinforcement (0.3% in both directions).
Highlights
The focus of this study is to evaluate the possibility of replacing minimum web reinforcement in deep beams with randomly distributed macro fibers for similar or improved performance
AllAll thethe tested specimens failedfailed by forming a diagonal crack joining inner the edgeinner of edge of tested specimens by forming a diagonal crackthe joining the support plate and the outer edge of the loading plate, which is typically mentioned the support plate and the outer edge of the loading plate, which is typicallyinmentioned this paper as a critical crack
The provision of web reinforcement or discrete fibers is essential in deep beams to improve their performance
Summary
Reinforced concrete (RC) deep beams are commonly used in tall buildings, bridges, and marine structures. Deep beams have significantly higher shear capacity than slender RC beams due to their small shear span-to-effective depth ratio (a/d ≤ 2.0), where a is shear span of the beam and d is the effective depth. Higher strength in deep beams is possible due to the arching action, which leads to high-stress concentrations and non-linear strain distribution. Bernoulli’s hypothesis of linear strain distribution is no longer valid [1,2] in the analysis of RC deep beams. The disturbed region of the deep beam is designed based on empirical methods or thumb rules.
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