• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.35-44
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• 2017

본 연구에서는 국내 콘크리트구조기준(2012)에서 규정하고 있는 최소철근량 이하로 보강된 보에 강섬유를 혼입한 강섬유보강철근콘크리트보의 휨파괴 실험을 수행하였다. 실험변수는 철근비와 강섬유의 혼입량으로 하였다. 철근보강비는 최소철근량의 44%, 66%, 78%와 100%로 하였으며, 강섬유의 혼입량은 0.25%, 0.50%, 0.75% 및 1.00%이다. 실험결과, 강섬유는 균열저항성능을 크게 개선시키는 것으로 확인되었다. 또한, 하중저항성능의 관점에서 강섬유는 항복하중의 증가에 기여하지만 극한하중의 증가에는 거의 기여하지 못하는 것을 확인하였다. 강섬유로 인한 항복하중의 증가량은 철근 감소로 인한 항복하중의 감소량에 비하여 미미한 것으로 나타났다. 최소철근보에서 강섬유의 사용은 오히려 연성을 크게 감소시키는 것으로 확인되었다. 따라서 최소철근 휨부재에 강섬유를 사용하기 위해서는 연성도 확보를 위하여 철근비를 증가시켜야 하는 것으로 확인되었다.

• 한국건축시공학회지
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• 제3권1호
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• pp.85-91
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• 2003

This study aims to provide basic data that can be applied to construct real structures. For this, an experimental structure was manufactured to identify durability according to age of fiber-reinforced concrete which contains fiber reinforcement materials (polypropylene fiber, steel fiber, cellulose fiber) and structural property about flexural behavior and destruction of reinforced concrete beam, and a relation between load and deflection, crack and destruction according to increase of load and ductility capacity was examined. Fiber-reinforced concrete materials and other constructional materials were experimented and the result is presented as follows: The results obtained through material test of concrete and static experiment of members usings 1. The experiment shows that compressive strength of fiber-reinforced concrete was lower than that of non-reinforced concrete. 2. As a result of strength experiment according to different kinds of fiber, compressive strength of an experimented structure that contains cellulose fiber was the highest when age was 28. 3. When deflection of reinforced concrete beam was examined, it was reported that ductility capacity of the experimented structure that contains fiber-reinforced concrete was raise than that of non-reinforced concrete.

• 한국구조물진단유지관리공학회 논문집
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• 제13권1호통권53호
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• pp.161-168
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• 2009

본 연구에서는 강섬유보강 콘크리트의 시공성 및 품질향상 방안의 일환으로 고유동 자기충전 콘크리트(HSCC)에 형상비 및 길이를 달리한 강섬유(SF)를 혼입한 콘크리트를 제조하여 강섬유보강 일반콘크리트(CC)와 유동 및 강도 특성을 비교 검토하였다. 실험결과 SF를 혼입한 HSCC는 높은 유동성 및 점성의 영향으로 SF 자체의 뭉침현상이 발생하지 않아 강섬유보강 CC의 경우보다 유동성능 및 통과성능이 크게 향상 되었으며, 동일한 압축강도 범위에서 SF를 혼입하지 않은 HSCC의 경우보다 쪼갬 및 휨강도는 SF의 형상비와 관계없이 길이가 길어질수록 증가하는 경향이 나타났다. 이상의 실험결과를 통하여 강섬유를 혼입한 HSCC를 현장 적용할 경우 기존에 사용되고 있는 강섬유보강 CC의 경우보다 시공성 및 품질 향상이 가능할 것으로 판단된다.

• Computers and Concrete
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• 제24권1호
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• pp.63-71
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• 2019

Thermal energy from high temperatures can cause concrete damage, including mechanical and chemical degradation. In view of this, the residual mechanical properties of high-strength fiber reinforced concrete with a design strength of 75 MPa exposed to $400-800^{\circ}C$ were investigated in this study. The test results show that the average residual compressive strength of high-strength fiber reinforced concrete after being exposed to $400-800^{\circ}C$ was 88%, 69%, and 23% of roomtemperature strength, respectively. In addition, the benefit of steel fibers on the residual compressive strength of concrete was limited, but polypropylene fibers can help to maintain the residual compressive strength and flexural strength of concrete after exposure to $400-600^{\circ}C$. Further, the load-deflection curve of specimen containing steel fibers exposed to $400-800^{\circ}C$ had a better fracture toughness.

• Steel and Composite Structures
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• 제39권3호
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• pp.307-318
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• 2021

Utilizing fibers is an effective way to avoid the brittle behavior of the conventional concrete and can enhance its ductility. In particular, propylene fibers can improve concrete properties, including energy absorption, physical and mechanical properties, controlling shrinkage cracks. The increase of fiber density leads to an increase of the overlapping surface of the fiber of concrete and, in turn, a decrease of cracks developed in the concrete. However, the workability of fiber reinforced concrete tends to be lower than the conventional concrete owing mainly to the hairline thickness and excessive concentration of fibers. The low slump of concrete impedes the construction of reinforced concrete members. In this research, we study if the utilization of magnetic water can alleviate the workability issue of young fiber reinforced concrete. To this end, the compressive and flexural strength of four types of concrete (conventional concrete, fiber reinforced concrete, magnetic concrete, magnetic fiber-reinforced concrete) is studied and compared at three different ages of 7, 14, and 28 days. In order to study the influence of the fiber density and length, a study on specimens with three different fiber density (1, 2, 5 kg of fiber in each cubic meter of concrete) and fiber length (6, 12, 18 mm) is undertaken. The result shows the magnetic fiber concrete can result in an increase of the flexural and compressive strength of concrete at higher ages.

• Advances in concrete construction
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• 제10권3호
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• pp.257-269
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• 2020

The aim of this study is to investigate the flexural performance of hybrid fiber reinforced self-compacting concrete (HFRSCC) having different ratio of micro and macro steel fiber. A total of five mixtures are prepared. In all mixtures, the sum of the steel fiber content is 1% and also water/binder ratio is kept constant. The amount of high range water reducer admixture (HRWRA) is arranged to satisfy the workability criteria of self-compacting concrete. Four-point bending test is carried out to analyze the flexural performance of the mixtures at 28 and 56 curing days. From the obtained load-deflection curves, the load carrying capacity, deflection and toughness values are investigated according to ASTM C1609, ASTM C1018 and JSCE standards. The mixtures containing higher ratio of macro steel fiber exhibit numerous micro-cracks and, thus, deflection-hardening response is observed. The mixture containing 1% micro steel fiber shows worst performance in the view of all flexural parameters. An improvement is observed in the aspect of toughness and load carrying capacity as the macro steel fiber content increases. The test results based on the standards are also compared taking account of abovementioned standards.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.99-104
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• 2000

In this paper, the crack properties fiber reinforced concrete(SFRC) beams by experimental method is discussed. The major role played by the steel fiber occurs in the post-cracking zone, in which the fibers bridge across the cracked matrix. Because of its improved ability to bridging cracks, SFRC has better crack properties than that of reinforced concrete(RC). Crack properties are influenced by longitudinal reinforcement ratio, volume and type of steel fibers, strength of concrete and the stress level. Crack width and number of cracks in SFRC beams have been evaluated from experimental test data at various levels of stress for the tested beams.

• Advances in concrete construction
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• 제5권1호
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• pp.75-86
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• 2017

An experimental work was carried out to study the effect of hybrid fiber on the tension stiffening and cracking characteristics of geopolymer concrete (GPC). A total of 24 concentrically reinforced concrete specimens were cast and tested under uniaxial tension. The grade of concrete considered was M40. The variables mainly consist of the volume fraction of crimped steel fibers (0.5 and 1.0%) and basalt fibers (0.1, 0.2 and 0.3%). The load deformation response was recorded using LVDT's. At all the stages of loading after the first cracking, crack width and crack spacing were measured. The addition of fibers in hybrid form significantly improved the tension stiffening effect. In this study, the combination of 0.5% steel fiber and 0.2% basalt fiber gave a better comparison than the other combinations.

• 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.

• 콘크리트학회논문집
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• 제20권4호
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• pp.531-539
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• 2008

본 연구에서는 강섬유보강 고강도콘크리트의 휨강도와 휨인성을 평가하기 위하여 실험을 수행하였으며, 이러한 실험 결과와 기존 연구자들의 실험 결과를 추가하여 강섬유보강 고강도콘크리트의 휨거동 특성을 분석하였다. 고강도 강섬유 콘크리트의 휨거동 특성은 강도와 인성으로 평가할 수 있으며, 이러한 특성은 콘크리트의 압축강도, 강섬유 혼입률 및 형상비, 강섬유계수와 같은 요소에 의해 영향을 받는 것으로 파악되었다. 아울러 기존 연구자에 의해 제안된 휨강도 산정식의 유효성을 평가하였으며, 강섬유 콘크리트의 휨강도는 콘크리트의 압축강도, 강섬유 혼입률 및 형상비, 강섬유계수와 같은 구조변수의 영향을 모두 고려하여 평가하는 것이 합리적이라고 판단되었다. 최종적으로 본 연구에서는 강섬유 혼입에 따른 휨강도의 상승분과 주요 구조변수간의 상관관계를 분석함으로써 보다 합리적인 휨강도 산정식을 제시하였다.