• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.311-318
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• 1995

Increases in strength and ductilities of steel fiber reinforced concrete(SFRC) under direct tension and compression result in improvements of flexural behavior of reinforced steel fibrous concrete beam(RSFCB) Use of hooked steel fibers in stead of round steel fibers enhances futher the structural porperties of a beam due to their greater mechanical bond resistance compared to that of round steel fibers. Flexural strength, initial stiffness ductility and failure mechani는 of RSFCB are dependent upon material and structural parameters and among which are the volume fraction of fibers, reinforcement ratio, and casting depth of SFRC in a beam section. The flexural behavior of RSFCB's are examined experimentally in this study and some conclusions are made regarding those effects of main material and structural parameters on the overall behavior of RSFCB.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.567-572
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• 1999

Experimental study was conducted to investigate the flexural-shear behavior of hooked steel fiber reinforced high strength concrete (SFRHC) beams. Twenty beams with shear span-depth ratio of 1.45 were tested, of which variables were the contents of steel fiber with aspect ratio of 60, tension reinforcement ratio and concrete compressive of 60MPa and 80MPa. Test results has shown that shear failure of the beams were changed into flexural-shear failure or flexural failure according to increasing steel fiber content, that SFRHC with slump of 15cm over and fiber volume ratio of 1.5% was possible in practice, and that proper volume ratio of steel fiber was 1.5%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.333-336
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• 2005

This paper presents a comparative evaluation of eight different types of steel fibers used as reinforcing material in concrete beams. The fibers which used ultra-strength steel fiber reinforced concrete were fiber length of 30 to 60mm, aspect ratio of 43 to 86, W/B ratio 0.16 to 0.30, fiber types of both ends hooked and straight shape and fiber volume fraction of 1 to 5$\%$. As for the test results, it estimated the influence of fiber volume, length and aspect ratio on the mechanical properties of high toughness concrete, the mechanical properties improved according to increase fiber volume, to increase aspect ratio and to long fiber length. And the resonable fiber volume in high toughness concrete was analyzed 2$\%$ based on the results of mechanical properties.

• 한국건축시공학회지
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• 제13권1호
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• pp.20-28
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• 2013

Flexure toughness of Steel Fiber Reinforced Concrete (SFRC) shows a time-dependent characteristic due to the hydration process of the cement matrix in the SFRC system. The effect of two important factors, water/cement (w/c) ratio and fiber volume fraction, on the flexure toughness development of SFRC were investigated. Three different SFRC mixtures with hooked-end steel fibers were tested using a four-point bending testing configuration. Each mixture was tested at five different ages. The results showed that the post-peak toughness of SFRC developed at an earlier age than the first-crack toughness.

• Structural Engineering and Mechanics
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• 제49권4호
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• pp.449-461
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• 2014

The use of low-ductility welded wire fabric (WWF) as a main tensile reinforcement in concrete slabs compromises the ductility of concrete structures. Lower ductility in concrete structures can lead to brittle and catastrophic failure of the structures. This paper presents the experimental study carried out on eight simply supported one-way slabs to study the structural behavior of concrete slabs reinforced with low-ductility WWF and steel fibers. The different types of steel fibers used were crimped fiber, hooked-end fiber and twincone fiber. The experimental results show that the ductility behavior of the slab specimens with low-ductility reinforcement was significantly improved with the inclusion of $40kg/m^3$ of twincone fiber. Distribution of cracks was prominent in the slabs with twincone fiber, which also indicates the better distribution of internal forces in these slabs. However, the slab reinforced only with low-ductility reinforcement failed catastrophically with a single minor crack and without appreciable deflection.

• Advances in concrete construction
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• 제9권4호
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• pp.367-374
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• 2020

Concrete surfaces, industrial floors, sidewalks, roads and parking lots are typically subjected to abrasions. Many studies indicated that the abrasion resistance is directly related to the ultimate strength of the cured concrete. Chemical reactions, freeze-thaw cycles, and damages under abrasion are among many factors negatively affecting the concrete strength and durability. One of the major solutions to address the abrasive resistance of the concrete is to use fibers. Fibers are used in the concrete mix to improve the mechanical properties, strength and limit the crack propagations. In this study, implementation of the steel fibers in concrete to enhance the abrasive resistance of the concrete is investigated in details. The abrasive resistance of the concrete with and without steel fibers is studied with the sandblasting technique. For this purpose, different concrete samples are made with various hooked steel fiber ratios and investigated with the sandblasting method for two different strike angles. In total, 144 ASTM verified cube samples are investigated and it is shown that those samples with the highest steel fiber ratios have the highest abrasive resistance. In addition, the experiments determine that there is a meaningful correlation between the steel fiber percentage in the mix, strike angle and curing time which could be considered for improving structural behavior of the fiber-reinforced concrete.

• 대한토목학회논문집
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• 제12권4호
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• pp.95-106
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• 1992

강섬유의 형태가 콘크리트의 휨거동에 미치는 영향을 알아 보기 위하여 5종의 강섬유를 사용한 실험을 실시하였다. 강섬유 혼입율은 1~2%로 변화를 주었고 전단 스팬비와 철근비는 고정하였다. 형태가 다른 강섬유의 보강 효과를 비교 분석하기 위한 방법으로 섬유 보강 효과 지수를 채택하였고, 인성 효과를 분석하기 위하여 유효 인성 지수를 제안하였으며, 이들 지수들은 강섬유 보강 효과를 비교 분석하는데 유용한 방법으로 평가되었다. 실험 결과에 의하면 강섬유 혼입율은 양단이 hook 형태인 강섬유의 경우에는 1% 이내가 효과적이며, dog bone 형태인 강섬유는 1~2%, 기타 강섬유는 2% 정도가 적절하였다. 강섬유의 혼입으로 인한 휨강도 및 파괴인성의 증진 효과는 무근 콘크리트보의 경우가 철근 콘크리트보의 경우보다 크게 나타났다. 또한 강섬유의 형태에 의한 휨강도와 인성의 증진 효과는 양단이 hook나 dog bone(paddled)형태의 강섬유가 섬유 혼입율이 상대적으로 낮음에도 straight나 crimped 및 wavy 형태보다 우수한 것으로 판명되었다.

• International Journal of Concrete Structures and Materials
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• 제3권2호
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• pp.119-126
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• 2009

This paper provides a brief summary of the performance of an innovative slip hardening twisted steel fiber in comparison with other fibers including straight steel smooth fiber, high strength steel hooked fiber, SPECTRA (high molecular weight polyethylene) fiber and PVA fiber. First the pull-out of a single fiber is compared under static loading conditions, and slip rate-sensitivity is evaluated. The unique large slip capacity of T-fiber during pullout is based on its untwisting fiber pullout mechanism, which leads to high equivalent bond strength and composites with high ductility. Due to this large slip capacity a smaller amount of T-fibers is needed to obtain strain hardening tensile behavior of fiber reinforced cementitious composites. Second, the performance of different composites using T-fibers and other fibers subjected to tensile and flexural loadings is described and compared. Third, strain rate effect on the behavior of composites reinforced with different types and amounts of fibers is presented to clarify the potential application of HPFRCC for seismic, impact and blast loadings.

• 콘크리트학회논문집
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• 제24권4호
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• pp.369-379
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• 2012

비산물체의 충돌 및 폭발, 테러 등의 극한하중에 의한 구조물의 붕괴는 재산상의 손실뿐만 아니라 다수의 인명피해를 유발한다. 일반적으로 콘크리트는 타 건설재료에 비해 충격 및 폭발 하중에 우수한 저항성능을 지니고 있다고 알려져 있으나, 준-정적(quasi-static)하중과는 달리 높은 변형률 속도를 갖는 극한하중을 고려하지 않고 설계된 기존의 콘크리트 구조물은 예상치 못한 극한하중에 노출될 경우 상당히 위험할 수 있다. 이 연구에서는 콘크리트 보의 충격저항성능을 향상시키기 위해 길이 30 mm의 번들형 양단 hooked type의 강섬유를 전체 부피의 0%에서 1.5%까지 혼입하여 정하중 및 충격하중 휨 실험을 수행하고, 그 성능을 평가하였다. 실험 결과 강섬유의 혼입률을 증가시킬 경우 정하중뿐만 아니라 충격하중에서도 휨강도와 연성 등 휨 저항성능이 크게 향상되는 경향을 보였다. 강섬유를 인장부에 집중적으로 혼입한 층 구조 콘크리트 보의 경우에는 동일한 양의 섬유를 보 전체에 타설한 시편에 비해 휨 저항성능이 향상되는 것으로 나타났다. 또한, 강섬유 보강 콘크리트의 재료적 비선형성을 고려하여 단자유도계(sing degree of freedom, SDOF) 시스템의 해석 알고리즘을 구성하고 실험 결과와 비교하였으며, 비교적 정확하게 최대 처짐을 예측하는 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.884-894
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• 2015

Background: Fibers in concrete resist the growth of cracks and enhance the postcracking behavior of structures. The addition of fibers into a conventional reinforced concrete can improve the structural and functional performance of safety-related concrete structures in nuclear power plants. Methods: The influence of fibers on the ultimate internal pressure capacity of a prestressed concrete containment vessel (PCCV) was investigated through a comparison of the ultimate pressure capacities between conventional and fiber-reinforced PCCVs. Steel and polyamide fibers were used. The tension behaviors of conventional concrete and fiber-reinforced concrete specimens were investigated through uniaxial tension tests and their tension-stiffening models were obtained. Results: For a PCCV reinforced with 1% volume hooked-end steel fiber, the ultimate pressure capacity increased by approximately 12% in comparison with that for a conventional PCCV. For a PCCV reinforced with 1.5% volume polyamide fiber, an increase of approximately 3% was estimated for the ultimate pressure capacity. Conclusion: The ultimate pressure capacity can be greatly improved by introducing steel and polyamide fibers in a conventional reinforced concrete. Steel fibers are more effective at enhancing the containment performance of a PCCV than polyamide fibers. The fiber reinforcementwas shown to bemore effective at a high pressure loading and a lowprestress level.