• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.651-658
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• 2010

Sixteen concrete mixes reinforced with hybrid steel-polybinyl alcohol (PVA) fibers and a control concrete mix with no fiber were tested in order to examine the effect of the micro and macro fibers on the slump and different mechanical properties of concrete. Main variables investigated were length and volume fraction of steel and PVA fibers. The measured mechanical properties of hybrid fiber reinforced concrete were analyzed using the fiber reinforcing index and compared with those recorded from monolithic steel or PVA fiber reinforced concrete. The initial slump of hybrid fiber reinforced concrete decreased with the increase of the aspect ratio and the volume fraction of fibers. In addition, splitting tensile strength, modui of rupture and elasticity, and flexural toughness index of concrete increased with the increase of the fiber reinforcement index. Modulus of rupture and flexural toughness index of hybrid fiber reinforced concrete were higher than those of monolithic fiber reinforced concrete, though the total volume fraction of hybrid fibers was lower than that of monolithic fiber. For enhancing the flexural toughness index of hybrid fiber reinforced concrete, using the steel fiber of 60 mm length was more effective than using the steel fibers combined with 60 mm and 30 mm lengths.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.1-6
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• 2002

In order to study the characteristics of fiber reinforced bearing, the steel plates of laminated rubber bearing were replaced with fibers which have same effects of steel plates. The comparison of vertical test and horizontal test of laminated rubber bearing and fiber reinforced bearing shows that the effective damping of fiber reinforced bearing is higher than laminated rubber bearing. This result implies the high energy dissipation ability of fiber reinforced bearing under earthquake excitation. These fiber reinforced bearing can be applied to the low-coast building.

• Korean Journal of Materials Research
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• v.5 no.3
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• pp.316-323
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• 1995

페놀수지 결합재에 PAN섬유(PF), PAN계 탄소섬유(CF) 그리고 아라미드 섬유(AF)를 보강재로 사용하여 단일섬유 보강복합재를 제조하였으며 이들 섬유를 각각 두 종류씩 혼성하여 혼성섬유 보강복합재를 제조하였다. 각 보강복합재를 섬유의 보강분율에 따른 마찰 및 마모특성을 시험하였다. CF 보강복합재(CFRP)가 마찰계수와 마모량이 가장 낮게 나타났으며, PF 보강복합재(PFRP)는 가장 높은 마찰계수와 마모량을 나타내었다. PF에 CF나 AF를 보강한 혼성복합재의 경우 마찰계수가 0.311~0.328로 혼성비에 따라서는 큰 차이를 보이지 않은 반면, PF의 보강분율이 증가할수록 마모량은 증가하였다. CF와 AF를 보강한 혼성복합재의 마찰계수는 0.264~0.309로 가장 낮게 나타났고, AF의 보강분율이 증가함에 따라 마찰계수는 증가하는 양상을 나타내었으며, 가장 적은 마모량과 함께 안정된 마모형태를 보였다.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.607-614
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• 2015

This study evaluated the flexural performance of steel and PP fiber reinfroced shotcrete using round panel test according to ASTM that can consider the actual stress of fiber reinforced shotcrete in tunnel and under ground structures. The results of round panel test are converted to the square panel test results according to the EFNARC. The energy absorptions of each fiber reinforced shotcrete were classified according to the EFNARC toughness classification. Test results show that the PP fiber reinforced shotcrete has better flexural performance compared with the steel fiber reinforced shotcrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.225-232
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• 2014

This paper concerns the mechanical properties of recycled plastic fiber-reinforced concrete. It presents experimental research results of recycled fiber-reinforced concrete with fiber volume fractions of 0, 0.5, 1.0, 1.5, and 2%. Experiments were performed to measure mechanical properties such as compressive strength, elastic modulus, tensile strength, and length changes. The results show that both compressive strength and elastic modulus decreased as fiber volume fraction increased. In addition, the experimental results show that recycled fiber-reinforced concrete is in favor of split tensile strength, flexural tensile strength, characteristic regarding crack mouth opening displacement, and length changes. The results of this study can be used to provide realistic information for modeling of mechanical properties in recycled plastic fiber-reinforced concrete in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.249-257
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• 2008

Various methods have been used to reinforce the cementitious material such as mortar and concrete that have weak tensile strength. Major reinforcing method is to mix matrix with fibers which have strong tensile strength. Recently, micro-fiber reinforced mortar has been studied which removes coarse aggregate and uses micro-fiber with small diameter in order to homogenize the matrix properties and maximize the performance of fiber. Performance of micro-fiber reinforced mortar showing multiple cracking behavior is hardly represented only by the flexural toughness. Therefore, This paper reports the cracking behavior as well as mechanical behavior for various mixtures which have different fiber type and mixture proportions to find the proper parameter representing the cracking characteristic. Correlations between flexural toughness and various cracking characteristics such as cracking area, width and number are explored. As a result, it is found that flexural toughness, volume of fiber and number of cracks are suitable for representing the characteristics of micro-fiber reinforced mortar.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.79-86
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• 2012

Though steel reinforcing bars are the most widely used tensile reinforcement, corrosion problems are encountered due to the exposure to aggressive environments. As an alternative material to steel, the fiber reinforced polymers have been used as reinforcement in concrete structures. However, bond strength of FRP rebar is relatively low compared to steel rebar. It has been reported that fibers in matrix can resist crack growth, propagation and finally result in an increase of toughness. In this study, high-strength concrete reinforced with structural fibers was produced to enhance interfacial bond behavior between FRP rebar and concrete matrix. The interfacial bond-behaviors were investigated from a direct pullout test. The test variables were surface conditions of GFRP bars and fiber types. Total of 54 pullout specimens with three different types of bars were cast for bond strength tests. The bond strength-slip responses and resistance of the bond failure were evaluated. The test results showed that the bond strength and toughness increased according to the increased fiber volume.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.213-220
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• 2004

The purpose of this study is to evaluate the shear strength of SFRC beam that has no stirrups by steel fiber strengthening factor. To achieve the goal of this study, two stage investigation, which is material and member level, is studied with literature and experimental side. From the reviewing of previous researches and analyzing of material and member test results, strengthening parameter of SFRC is defined as steel fiber coefficient. Based on above results, steel fiber strengthening factor is proposed. And by reviewing the proposed equation of shear strength estimation, equation of Shin was well estimated the shear strength of SFRC beams. Therefore, shear strength equation of SFRC, which is composed by Shin's Eq. and steel fiber strengthening factor, is proposed by regression analysis of test results.

• Journal of the Korea Institute of Building Construction
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• v.11 no.4
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• pp.326-332
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• 2011

Carbon, Aramid, Boron and Glass fibers are used as fibrous materials to promote structural bearing strength. Of these fiber types, carbon fiber is the most commonly used material, and is characterized by having a one-way direction, which is strengthened by tensile strength due to the attached direction only, while other types of fibers are two-way. Therefore, when applied in the field, the attachment direction of fiber is a very important factor. However, when fiber direction is not mentioned in the design drawing, there sometimes is no improvement in structural strength, as the fiber is being installed by a site engineer or workers who lack structural knowledge. The purpose of this study was to propose an optimal direction of carbon fiber through a comparison & analysis of reinforcing efficiency with reinforced experimental columns that used carbon fibers in each of the inclined, horizontal and vertical directions. According to the results, horizontal direction in the reinforced column was improved by 153.43%, but vertical direction was 104.61% only, and it was understood this was due to increased tensile strength along the fiber direction. For this reason, it is necessary to include information regarding fiber direction in design and site management.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.211-217
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• 2012

In this paper, experimental tests and theoretical studies were carried out to evaluate the tensile behavior of the sprayed FRP composite with chopped glass fiber. For this, a series of tensile strength tests with various strain rates were conducted on the specimens of the matrix and sprayed FRP composite. Sprayed FRP composite contained chopped glass fibers with fiber length of 15mm and a specific volume fraction of fibers of 25 %. An inverse simulation was conducted to simulate the strain rate sensitivity based on the present experimental data of the epoxy resin. The simulated viscosity value is adapted to the micromechanics-based viscoelastic damage model(Yang et al., 2012), and the overall tensile behavior of sprayed FRP composites is predicted. It was seen from the comparative study between present experimental data and predication results that the proposed methodology can be used to predict the viscoelastic behavior of the sprayed FRP composite.