• 한국세라믹학회지
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• 제33권11호
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• pp.1187-1194
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• 1996

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.55-60
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• 2001

Influencing factors on flexural toughness of ring-type fiber reinforced concrete(RSFRC) are investigated. An experiment proceeding ASTM C 78 is peformed to make a comparison between ring-type fibers and double-hook type fibers. Most specimen with ring type fibers have failed by the cone type failure, while discrete hook type fibers have failed by fiber pullout. For the hook-type fiber reinforced concrete(SFRC), the first crack load increases, as the fiber mixing volume increases. Aspect ratio(fiber length/fiber diameter) is critical for hook type fibers, so the flexural toughness increases significantly, as the length of fiber increases. However, for the ring type, the toughness indices Increase as the number of fibers in the specimen increases. Since there is no bond problem between the ring fiber and the concrete matrix, the aspect ratio does not affect the performance of the composite material with the newly developed steel fibers. Influencing factors with respect to flexural toughness RSFRC were observed to be ring diameter, diameter of steel fiber and fiber content.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.625-628
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• 2006

In this study, the beam which is repaired as high toughness cementitious composites evaluated on flexural performance. As for the test results, it was found that high toughness performance of beams of the repair as high toughness cementitious composites showed more better than the existing repair method and demonstrated about 95% semi-reinforcement to compare with reinforcement of carbon fiber sheets of one layer without interface and brittle failure. Therefore, appling on using PVA fiber reinforced high toughness cementitious composites, the repaired concrete structures can be increased to flexural performance.

• 한국생산제조학회지
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• 제9권6호
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• pp.170-177
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• 2000

Dense $Al_2$O$_3$-30%TiC and Si$_3$N$_4$ ceramic tool materials with various grain size were produced by sintering-HIP treatment and by gas-pressure sintering. The fracture toughness was measured by indentation fracture and indentation strength method for both ceramics with various grain size. The effect of the grain size on the fracture toughness was evaluated, and the correlation between fracture toughness and mechanical properties such as hardness, Young\`s modulus and flexural strength of these ceramic were also investigated. The highest fracture toughness of around 6.7 MPa.m(sup)1/2 was obtained in Si$_3$N$_4$ ceramics with grain size of 1.58${\mu}{\textrm}{m}$. With a larger grain size of $Al_2$O$_3$-30%TiC and Si$_3$N$_4$ ceramics, the fracture toughness was generally increased. The increased fracture toughness of these ceramic also improved the flexural strength although the hardness decreased considerably. Similar results were obtained in grain size and mechanical properties on both $Al_2$O$_3$-30%TiC and Si$_3$N$_4$ ceramic tool materials.

• 콘크리트학회지
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• 제8권5호
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• pp.163-170
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• 1996

셀룰로우스 섬유는 강도와 강성측면에서 우수하고 동시에 적은 에너지로 가공이 가능하며, 또한 가격 면에서도 유리하고 풍부한 양으로 인해 시멘트의 보강재료로서 적당하다. 셀룰로우스 섬유 시멘트 복합체는 일반적으로 슬러리-탈수 가공에 의해 생산되며 평면이나 곡면 등의 시멘트 복합제품으로 얇은 판을 만드는데 주로 사용되어진다. 본 연구에서는 셀룰로우스 섬유 혼입률과 여러 가지 수분상태에서의 강도 특성을 실험에 의해 고찰하였다. 이들 시멘트 복합체의 강도효과에 대한 실험결과들의 검증을 위하여 통계학적인 분산분석과 다중비교에 의한 분석을 수행하였다. 휨강도는 섬유 혼입률이 약 8%까지 상승할 때 증가하였으며, 휨인성은 섬유 혼입률의 증가에 따라 증가하였다. 수분함유량은 휨강도에 중요한 요인으로 작용하였는데, 수분 함유량의 증가는 휨강도의 감소를 가져온 반면, 휨인성의 증가를 보여주었다. 시멘트 복합체에 포졸란 재료를 사용하였을 경우 수분에 의한 영향은 크지 않은 것으로 나타났으며 약간의 휨인성의 감소와 더불어 휨강도의 증가를 보였다.

• 콘크리트학회논문집
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• 제26권4호
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• pp.483-489
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• 2014

이 연구에서는 ASTM C 1609을 따라서 비정질 강섬유보강콘크리트의 휨실험을 수행하였고, 이를 바탕으로 휨성능을 평가하였다. 비정질 강섬유는 기존의 일반 강섬유와 달리 얇은 두께, 거친 표면의 특성을 가지고 있다. 주요한 실험변수는 섬유 종류(비정질 강섬유, 일반 강섬유), 섬유 혼입률(0.25, 0.50, 0.75%) 그리고 콘크리트 압축강도(27, 50 MPa)이다. 실험 결과에 근거하여 비정질 강섬유와 일반 강섬유보강콘크리트의 휨강도와 휨인성을 분석하였고, 그 결과 일반 강섬유보강콘크리트의 경우 주로 휨인성이 증가하였으나 비정질 강섬유보강콘크리트의 경우 휨강도와 인성을 모두 증가하는 것으로 나타났다.

• Advances in concrete construction
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• 제13권 2호
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• pp.123-132
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• 2022

This paper aims to adapt Multilinear regression (MLR) to predict the strength and toughness of SIFCON containing various pozzolanic materials. Slurry Infiltrated Fibrous Concrete (SIFCON) is one of the most common terms used in concrete manufacturing, known for its benefits such as high ductility, toughness and high ultimate strength. Assessment of compressive strength (CS.), flexural strength (F.S.), splitting tensile strength (STS), dynamic elasticity modulus (DME) and impact energy (I.E.) using the experimental approach is too costly. It is time-consuming, and a slight error can lead to a repeat of the test and, to solve this, alternative methods are used to predict the strength and toughness properties of SIFCON. In the present study, the experimentally investigated SIFCON data about various mix proportions are used to predict the strength and toughness properties using regression analysis-multilinear regression (MLR) models. The input parameters used in regression models are cement, fibre, fly ash, Metakaolin, fine aggregate, blast furnace slag, bottom ash, water-cement ratio, and the strength and toughness properties of SIFCON at 28 days is the output parameter. The models are developed and validated using data obtained from the experimental investigation. The investigations were done on 36 SIFCON mixes, and specimens were cast and tested after 28 days of curing. The MLR model yields correlation between predicted and actual values of the compressive strength (C.S.), flexural strength, splitting tensile strength, dynamic modulus of elasticity and impact energy. R-squared values for the relationship between observed and predicted compressive strength are 0.9548, flexural strength 0.9058, split tensile strength 0.9047, dynamic modulus of elasticity 0.8611 for impact energy 0.8366. This examination shows that the MLR model can predict the strength and toughness properties of SIFCON.

• 한국터널지하공간학회 논문집
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• 제21권3호
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• pp.433-452
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• 2019

본 연구는 구조용 합성섬유(PP섬유) 혼입량에 따른 숏크리트 보강성능과 적정한 평가방법에 관한 것으로, 강섬유($37.0kg/m^3$)와 구조용 합성섬유(PP섬유) 혼입량을 매개변수($5.0kg/m^3$, $7.0kg/m^3$, $9.0kg/m^3$)로 설정하여 숏크리트 압축강도, 휨강도 및 휨인성 시험을 수행하였다. 특히, 판상의 숏크리트 에너지 흡수능력을 평가하기 위하여 원형 패널 휨인성 시험(Road and Traffic Authority, RTA)을 수행하였다. 검토결과, 압축강도 및 휨강도는 강섬유 보강 숏크리트가 다소크나, 실질적인 숏크리트 보강성능를 나타내는 휨인성은 구조용 합성섬유(PP섬유) 보강 숏크리트가 큰 것으로 분석됨에 따라, 강섬유 보강 숏크리트 대비 동등 이상의 보강효과를 발휘하는 것으로 검토되었다. 또한, 구조용 합성섬유(PP섬유) 혼입량에 따른 휨인성 및 에너지 흡수능력 상관관계에 의하면, 보시편 휨인성 시험(KS F 2566)의 허용기준 3.0 MPa이하조건에서 에너지 흡수능력이 발휘(A등급: 2.55 MPa = 202J, B등급: 2.72 MPa = 282J, C등급: 3.07 MPa = 403J)되는 것으로 검토되었다. 국내 터널현장에서 보수적으로 측정되는 강도개념의 숏크리트 휨인성(>3.0 MPa)을 본 연구의 숏크리트 에너지 흡수능력 상관관계로 지보성능을 평가할 경우, 보다 실질적이고 신뢰도 높은 숏크리트 지보성능 평가가 가능할 것으로 판단된다.

• Computers and Concrete
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• 제8권3호
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• pp.357-369
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• 2011

In this study, effect of steel fibers on toughness and some mechanical properties of concrete were investigated. Hooked-end steel fibers were used in concrete samples with three volume fractions (${\nu}_f$) of 0.5%, 0.75% and 1% and for two aspect ratios (l/d) of 45 and 65. Compressive and flexural tensile strength and modulus of elasticity of concrete were determined for cylindrical, cubic and prismatic samples at the age of 7 and 28 days. The stress-strain curves of standard cylindrical specimens were studied to determine the effect of steel fibers on toughness of steel-fiber-reinforced concrete (SFRC). In addition, the relationship between compressive strength and the flexural tensile strength of SFRC were reported. Finally, a simple model was proposed to generate the stress-strain curves for SFRC based on strains corresponding to the peak compressive strength and 60% of peak compressive stress. The proposed model was shown to provide results in good correlation with the experimental results.

• 산업기술연구
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• 제19권
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• pp.163-172
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• 1999

This study is conducted on the flexural toughness and flexural fatigue test to fine the mechanical properties of steel fiber reinforced rapid-set cement concrete. Experimental investigation is examined according to fiber contents(0, 0.4, 0.7, 1.0, 1.5%), fiber aspect ratio(58, 60, 83), fiber type (hooked, crimped fiber), and cement type (normal portland & rapid-set cement). The principal results obtained through this study are as follows; toughness and fatigue resistance tend to considerably increase with fiber contents, fiber aspect ration. And hooked fiber is improved better than crimped fiber. Concrete using rapid set cement is increased strength properties compared with concrete using normal portland cement, but relative strength properties behavior and fatigue resistance show a tendency to decrease a little.