• 콘크리트학회지
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• 제6권1호
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• pp.142-151
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• 1994

본 연구는 강섬유보강 콘크리트의 시공성 및 공학적 특성에 미치는 강섬유 길이의 영향과 실리카흄 및 플라이애시와 같은 콘크리트용 혼화재의 첨가에 의한 영향을 실험적으로 고찰한 것으로서 본 연구결과 낮은 물결함재비를 채용하고 고성능감수제를 사용함으로써 슬럼프 10(cm)의 유동성과 $600(kgf/\textrm{m}^2)$ 이상의 28일 압축강도를 갖는 강섬유보강콘크리트의 제조가 가능하였으며, 실리카흄의 사용은 강섬유보강콘크리트의 시공성 및 공학적 특성 개선에 유효한 인자로 나타났으며, 또한 강섬유보강콘크리트의 인장강도는 보통콘크리트에 비하여 높게 나타나 강섬유가 콘크리트의 인성증진에 기여 하는 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.128-129
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• 2014

In this study, flowability of the mortar added with length change and combination of steel and inorganic fiber has been tested to evaluate the performance of fiber-reinforced mortar. The following results could be made as the conclusion. Early age flow of the mortar has been decreased when fibers added. Slump also decreased with the adding of fibers. For the air content, comparing with Plain, all the specimens with fibers showed higher air content than Plain., Addition of every kinds fibers showed the similar EIS test results.

• Advances in concrete construction
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• 제14권5호
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• pp.299-307
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• 2022

Cement-based matrixes have low tensile strength and negligible ductility. Adding fibres to these matrixes will improve their mechanical properties and make these composites suitable for structural applications. Post-cracking tensile strength of steel fibers-reinforced cementitious composite materials is directly related to the number of transverse fibers passing through the crack width and the pulling-out behavior of each of the fibers. Therefore, the exact recognition of the pullout behavior of single fibers is necessary to understand the uniaxial tensile and bending behavior of steel fiber-reinforced concrete. In this paper, an experimental study has been carried out on the pullout behavior of 3D (steel fibers with totally two hooks at both ends), 4D (steel fibers with a total of four hooks at both ends), and 5D (steel fibers with totally six hooks at both ends) in which the fibers have been located either perpendicular to the crack width or in an inclined manner. The pullout behavior of the mentioned steel fibers at an inclination angle of 0, 15, 30, 45, and 60 degrees and with embedded lengths of 10, 15, 20, 25, and 30 millimetres is studied in order to explore the simultaneous effect of the inclination angle of the fibers relative to the alongside loading and the embedded length of fibers on the pullout response in each case, including the maximal pullout force, the slip of the maximum point of pullout force, pullout energy, fiber rupture, and concrete matrix spalling. The results showed that the maximum pullout energy in 3D, 4D, and 5D steel fibers with different embedded lengths occurs at 0 to 30° inclination angles. In 5D fibers, maximum pullout energy occurs at a 30° angle with a 25 mm embedded length.

• Computers and Concrete
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• 제16권5호
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• pp.759-774
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• 2015

This study simulates the flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with steel and glass fiber-reinforced polymer (GFRP) rebars. For this, micromechanics-based modeling was first carried out on the basis of single fiber pullout models considering inclination angle. Two different tension-softening curves (TSCs) with the assumptions of 2-dimensional (2-D) and 3-dimensional (3-D) random fiber orientations were obtained from the micromechanics-based modeling, and linear elastic compressive and tensile models before the occurrence of cracks were obtained from the mechanical tests and rule of mixture. Finite element analysis incorporating smeared crack model was used due to the multiple cracking behaviors of structural UHPFRC beams, and the characteristic length of two times the element width (or two times the average crack spacing at the peak load) was suggested as a result of parametric study. Analytical results showed that the assumption of 2-D random fiber orientation is appropriate to a non-reinforced UHPFRC beam, whereas the assumption of 3-D random fiber orientation is suitable for UHPFRC beams reinforced with steel and GFRP rebars due to disorder of fiber alignment from the internal reinforcements. The micromechanics-based finite element analysis also well predicted the serviceability deflections of UHPFRC beams with GFRP rebars and hybrid reinforcements.

• 콘크리트학회지
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• 제11권2호
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• pp.209-220
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• 1999

터널의 숏크리트 라이닝이나 포장 콘크리트 보강용으로 요접철망(wire mesh)을 대신해서 강섬유가 사용되고 있다. 본 연구에서는 강섬유 보강으로 인한 인성평가 대상 구조물을 slab panel 구조($60{\times}60{\times}10$cm)로 하고, 강섬유 혼입률은 콘크리트 용적의 0.5% ~ 2%로 다양화하였다. 이 때 사용한 강섬유는 Dramix ZC type으로 직경은 0.8mm, 길이는 60mm이다. 강섬유 효과의 상대평가를 위한 용접철망(wire mesh)보강은 상면, 하면, 상하면 보강으로 하였다. 이들 실험 결과를 각국의 인성 평가 방법으로 비교 검토한 결과 슬래브(slab) 시험체 적용을 위한 EFNARC의 방법은 25mm의 처짐까지 측정하는 것이 너무 큰 것으로 평가되었고, 보의 휨인성 평가법을 적용하여 검토한 결과에서는 Johnston(II)방법에 의한 $I_{5.5}$ 가장 적절하였으며, JCI-SF4방법에서 지간의 1/150까지 측정하는 것은 너무 작았다. 또한 강섬유로 용접철망(wire mesh)을 효과적으로 대치할 수 있음을 알 수 있었고, 인성효과에 유용한 강섬유 혼입량은 0.5% ~ 1%범위에 있는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.937-940
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• 2006

According to the analysis of tension failure mechanism of UHSC specimen, one modified model based on ACK model by the introduction of partial debonding energy of non-first cracks and by the application of steel fiber number on unit area is presented in this paper. It can be used to explain the evolution mechanism of multiple cracking and pseudo strain hardening of UHSC. From the numerical results, to increase steel fiber length and to reduce steel fiber diameter in some region all can reduce the fiber volume fraction with the same multiple cracks for economic design of UHSC.

• 콘크리트학회논문집
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• 제21권3호
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• pp.303-310
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• 2009

CFRP (carbon fiber reinforced polymer) 긴장재는 PC 강연선의 부식문제를 해결하기 위해 대안으로 사용될 수 있다. CFRP 긴장재를 콘크리트구조물에 적용하기 위해서는 부착강도, 전달길이, 정착길이와 같은 재료적 특성이 명확히 결정되어야 한다. 특히 프리텐션 콘크리트 부재에 CFRP 긴장재가 적용될 경우 전달길이는 긴장력 도입에 있어서 중요한 요소가 된다. 본 연구에서 개발된 CFRP 전달길이 및 정착길이를 산정하기 위해 프리텐션 보 9개를 제작하였다. 전달길이 실험결과, 긴장력 25%인 경우는 34D, 긴장력 50%인 경우는 55D로 측정되었고, 긴장력이 커지면 전달길이가 증가하는 것으로 나타났다. 시간경과에 따른 전달길이 변화를 살펴보면, 긴장력의 크기에 따라 시간경과가 전달길이에 영향을 주는 것으로 나타났다. 보강재 특성계수 산정 결과, 본 연구에서 개발된 CFRP 긴장재의 보강재-특성 계수 ${\alpha}_t$는 2.3으로 PS강연선 (${\alpha}_t=2.4$)과 비슷한 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제4권4호
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• pp.161-169
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• 2000

Recycled aggregates were generated when concrete structures were dismembered. However, in concrete structures, because of durability, strength and toughness, recycled aggregates don't use generally. This study was done to use recycled aggregate in concrete structures. Problems of durability, strength, and toughness were caused troubles, when recycled aggregates were used, were solved as steel fibers and additives were added. Of course, steel fiber length, steel fiber contents, additive substitution, and recycled aggregate substitution were variables of this study. After flexural specimens($15{\times}15{\times}70cm$) with notch(45mm) were fabricated, basic strength tests were done and toughness was estimated using fracture mechanics parameters. The results suggest that JIC is a promising fracture criterion for all of these, while KIC(or GIC) almost certainly are not.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.415-416
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• 2010

본 연구는 강섬유를 혼입한 고강도 콘크리트의 파괴 특성을 보여준다. 실험에 사용된 강섬유는 결합제의 용적비에 대한 0.5%, 0.75%. 1%를 사용하였고, 노치길이는 0, 15, 40, 45mm로 변화를 주었다. 3점 휨시험을 통해 J-integral($J_{Ic}$), $K_{Ic}$, $G_F$ deflection strength 그리고 fracture energy를 구하였다. 그 결과 섬유의 혼입은 콘크리트의 fracture energy를 향상시키는 것을 알 수 있었다.

• Structural Engineering and Mechanics
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• 제66권4호
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• pp.439-444
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• 2018

This paper presents a numerical study on the behavior of continuous hollow steel beam strengthened using carbon fiber reinforced polymers (CFRP). Most previous studies on the CFRP strengthening of steel beams have been carried out on the steel beams with simple boundary conditions. No independent study, to the researcher's knowledge, has studied on the CFRP strengthening of square hollow section (SHS) continuous steel beam. However, this study explored the effect of the use of adhesively bonded CFRP flexible sheets on the behavior of the continuous SHS steel beams. Finite Element Method (FEM) has been employed for modeling. Eleven specimens, ten of which were strengthened using CFRP sheets, were analyzed under different coverage length, the number of layers, and the location of CFRP composite. ANSYS software was used to analyze the SHS steel beams. The results showed that the coverage length, the number of layers, and the location of CFRP composite are effective in increasing the ultimate load capacity of the continuous SHS steel beams. Application of CFRP composite also caused the ductility increase some strengthened specimens.