• Proceedings of the Korean Fiber Society Conference
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• 1996.10a
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• pp.539-544
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• 1996

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.281-287
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• 2011

GFRP rebars could be deteriorated by concrete alkalinity. This paper focuses on the investigation of durability of GFRP rebars with ribs exposed to alkaline environment of concrete. It has been reported that the milled E-glass fibers in the ribs of GFRP rebar can increase bond strength between GFRP rebars and the concrete. In this study, the effect of milled alkaline resistant glass fibers (milled AR glass) and milled E-glass in the ribs on the durability of GFRP rebar is investigated through ISS tests and moist absorption tests of the bare rebar. To accelerate the effect of the alkalinity, high temperature($40^{\circ}C$) was applied. According to the test results, mix ratio of milled glass fibers in the ribs by weight had significant effect on durability of GFRP rebars with ribs. It is because that the high mix ratio may leads more voids in the ribs due to lower workability and formability. On the other hand, changing fiber type in the ribs from E-glass to AR-glass had no improvements on ISS strength of the GFRP rebar. Therefore, it is found that determination of proper mix ratio of milled glass fiber in the mixture for the formation of the ribs of the GFRP rebar is important.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.25-37
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• 2019

This study confirms reinforcing effect of geosynthetics in the use of soil at higher water contents as a compaction material on compaction tests, field compaction tests, and numerical analysis. To verify a confined effect, a large mold(area ratio of rammer / mold = 0.19) larger than D compaction mold(area ratio of rammer / mold = 0.33) was performed for compaction. It showed that in the D compaction test, dry density were 0.5~0.6% increases and in the compaction test using the large mold, it were 2.4~3.7% increases at high water contents. It shows that when the area of compacted area is large enough, a confined effect could be arising from the reinforcement of geosynthetics even at high water contents. As a result of analyzing of compaction effects according to 'depth(z/B) from compacted surface' in the field, when not reinforced, the compaction state deteriorated due to the over-compaction and the compaction did not work well. However, when reinforcement of geosynthetics, restraint effect by geosynthetics occurs, it is confirmed that the compaction energy is effectively transferred to the compaction layer and the dry density is increased. Also, through the conceptual model of the behavior of geosynthetic and soil layer, the mechanism in the ground due to reinforcement of geosynthetics is presented and it is verified through finite element analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.2
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• pp.107-116
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• 2001

복합재 적층판은 중량에 비해 높은 강성과 강도가 요구되는 공학의 다양한 분야에서 매우 유용하다. 보강섬유 복합재의 공학적 활용이 활발해지고, 중량의 감소화가 설계의 중요한 목적이 됨으로써, 근래 복합재 구조물들의 최적화 설계의 중요성이 대두되고 있다. 그러나 복합재 적층 구조물 재료의 비등방성에 의해 해석과 설계가 매우 어렵다. 본 연구에서는 수치적 최적화 방법과 유한요소법을 이용하여 보강섬유 복합재의 최적설계를 하였다. 복합재 적층판으로 이루어진 개단면 보에 있어서 보강섬유의 다양한 적층방향에 대한 거동의 영향을 규명하였다.

• Journal of Ocean Engineering and Technology
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• v.13 no.3B
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• pp.56-64
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• 1999

An experimental study was carried out to examine the structural behavior of reinforced concrete deep beams strengthened with aramid fiber sheets, carbon fiber sheets and plates, and to propose the reasonable strengthening method for the deteriorated R.C. deep beams. Results show that the most significant differences in behavior of reinforced concrete deep beams strengthened with fiber sheet and plate were mainly due to various fiber orientations and anchorage. Deep beams diagonally strengthened with carbon fibers show better performance compared with those of vertically, horizontally strengthened specimens and produce the increase in the shear resistance through the redistribution of internal forces after the initial cracks occur. However, strengthened deep beams without anchorages might show unreasonable, brittle peeling-off failure of fiber reinforcements.

• Journal of the KSME
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• v.30 no.2
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• pp.180-187
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• 1990

세라믹 복합재료의 크립 파괴거동의 근원이 되는 크립거동에 대한 해석은 현재까지 제시되어 있 는 것이 거의 전무하여, 세라믹 복합재료의 고온신뢰도는 실험에 의존되어 많은 시간과 노력이 소요된다. 여기서는 해석방법으로 advanced shear-lag 모델을 기본으로 세라믹 복합재료 특성을 고려하여 모델링 해석을 제시하였다. 여러 영향 인자들-보강섬유 형상비, 보강섬유 끝단의 간격, 계면에서의 미끄름계수, 단위 모델안의 보강섬유 배열이 크립거동에 미치는 효과에 대해 인자 변화효과(parametric study)를 관찰하여 실험에 의해 얻은 SiCw/A1$_{2}$O$_{3}$의 크립 결 과와 비교하였다. 모델링 해석을 통해 얻은 특정범위 내의 결과는 실험결과를 수용할 수 있으 므로 이 해석방법을 세라믹 복합재료 크립거동의 한방법으로 이용할 수 있으리라 사료된다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.87-88
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• 2018

In this study, the tensile properties of single and hybrid fiber reinforced cement composite according to strain rate was evaluated. Experimental results, in the strain rate 10^-6/s, fiber reinforced cement composite showed improved of tensile strength and decrease of strain at peak stress as SSF volume content increased. In the strain rate 101/s, the single and hybrid reinforced cement composite's tensile properties are improved, because of the improved bond strength between the fiber and matrix. And hybrid fiber reinforced cement composite showed high energy absorption capacity, because the SSF prevented the cracking and fracture of the surrounding matrix when during the HSF pull-out.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.135-142
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• 1999

A constitutive model was proposed to study the effects of fiber waviness on the elastic properties of unidirectional composite materials. The predictions showed that the degree of fiber waviness significantly affected the elastic properties of composite materials. A special fabrication technique was developed for thic composite materials with various fiber waviness ratios. Tensile, compressive and flexural tests were conducted to obtain the elastic properties of composite materials with fiber waviness experimentally. The experimental result were in good agreement with the predictions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.95-106
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• 1992

This paper presents a comparative evaluation of five different types of steel fibers used as reinforcing material in concrete beams. Two types of plain and RC beams were prepared to compare the relative flexural behavior. The fibers used were dog bone (paddled), both ends hooked. コ-type straight. crimped and wavy type with aspect ratio of 43 to 75. Fiber volume fraction of 1 to 2% were used while shear span to depth ratio (aid) and steel ratio p were fixed. Fiber reinforcement effect index Ef and effective toughness index Te were adopted to evaluate fiber reinforcing effects. The effect of fiber reinforcement on flexural strength is higher in plain beams than in RC beams. Hooked and dog bone type fibers were found to be more effective than the other type ones in enhancing the flexural strength and post-peak energy absorption capacity of concrete beams.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.387-394
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• 2016

This study was evaluated that fundamental quality properties in the mortar level, as part of a basic study for development of fiber reinforced concrete using basalt fiber. Mortar mixtures used in the experiments used the mortar using cement only and high volume fly ash mortar using fly ash of 50%, was evaluated by comparison. As a experiments results, high volume fly ash mortar using 50% fly ash was effective for improving fiber dispersibility than mortar using cement only, accordingly, it showed that fiber aggregation phenomenon has been greatly reduced. In addition, if the fly ash used much more than 50%, the compressive strength has been shown to decrease of about 30%, fiber length and mixing ratio of basalt fiber was found to have a greater effect on flow properties than mechanical properties.