• Composites Research
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• 제12권4호
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• pp.62-70
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• 1999

건축 구조물의 재령이 증가함에 따른 손상은 구조물의 안전성 및 신뢰성 확보에 매우 심각한 문제이다. 최근에는 이렇게 손상을 입은 콘크리트 구조물의 보수 보강을 위해 탄소섬유시트가 광범위하게 사용되고 있지만 탄소섬유시트를 보강한 콘크리트의 파괴기구가 명확하게 규명되지 않았다. 따라서 본 연구에서는 탄소섬유시트를 보강한 콘크리트의 손상거동 및 미시적 파손기구를 이해하기 위해 4가지 경우의 시험편, 즉 순수한 콘크리트, 철근 보강 콘크리트, 탄소섬유시트 보강 콘크리트, 철근과 탄소섬유시트 보강 콘크리트 시험편에 대하여 3점 굽힘 시험을 실시하였다. 이러한 시험편들의 파손기구를 명확히 하기 위해 음향방출기법이 사용되었으며 균열 발생, 성장을 모니터링하기 위해 2차원 AE 발생원 위치추정 기법이 적용되었다.

• Composites Research
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• 제33권4호
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• pp.191-197
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• 2020

본 연구에서는 향상된 내구성을 가진 고효율 전자파차폐용 랜덤배향 시트 소재를 개발하기 위해 구리(Copper: Cu)와 니켈 (Nickel: Ni)이 코팅된 탄소섬유(Carbon fiber: CF)와 같은 하이브리드 소재를 습식공정을 통해 제조 하였다. 제조된 시트 소재는 69.4~93.0 dB의 높은 전자파 차폐효율을 보여주었다. 또한 하이브리드 금속으로 코팅된 Ni-Cu/CFs 시트는 Ni표면의 유효한 부식저항성과 기계적 저항성 때문에 가혹한 화학적/열적 환경하에서 매우 우수한 내구성을 보여주었다. 이와 관련하여 Ni-Cu/CF 시트는 Cu/CF 시트와 비교하여 1.7배 긴 수명을 가지는 것을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.365-370
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• 2001

The repairing technique of surface wrapping concrete structural members using fiber composite sheet have been widely used. The research efforts have been limited to studying relative strength increase of repaired concrete structures rather than ductility improvement based on composite material effect and the interface effect between composite and concrete. The compression tests of CFS(carbon fiber sheet) reinforced concrete specimens with various cross-sectional shapes and laminate angles have been peformed. FEM algorithm considering various parameters will be performed based on the obtained data. The results will be discussed in detail.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.835-840
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• 2002

The purpose of this study is to analyze the reinforcement effect of the RC compressive member confined with carbon fiber sheets and to suggest better transverse confinement coefficient(k$_1$) than one's in the existing analysis equations. Showing amounts of CPS in terms of ratio of transverse reinforcement to cross-section, it comes to be possible to calculate the objective and quantitative reinforcement amounts and to estimate the overlapping length of CFS that can influence on all its confinement effect. The previous parameters were compared using the existing experimental test data, then analyzed for the merits and demerits of existing parameters through the coefficient of correlation(R). The proposed parameters were derived in such a way that established parameters and their combination were obtained from the analytical study and then determined by regression analysis using the previous test data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.653-658
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• 1997

Recently, carbon Fiber sheet (CFS) is frequently used for strengthening deteriorated concrete structures. To strengthening damaged structures, the property and characteristic of the bond between CFS and the concrete surface must be understood. The tensile test of single lap shear specimen was performed to study bond strength, bond stress distribution and stress transfer between CFS and concrete surface according to the bond length. Based on the test results, there were ultimate influence length (UIL) in which bond stress was distributed, and ultimate strain reduction ratio (USRR) by which strain was reduced linearly. Bond resisting force (BRF) was estimated by UIL and USRR, and which was compared with ultimate loads. According to the results of comparison, it was shown that ultimate bond strength could be estimated reasonablely by BRF.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.157-167
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• 2002

In most cases, quantity of reinforcement is determined without regard to the difference of initial strain, and status of damages when calculated the strengthening in flexure at beams. Thus, the purpose of this study is to investigate the flexural strengthening efficiency and behavior of RC beams strengthened with carbon fiber sheets(CFS) considering different status of damages. in this paper, a nonlinear analysis program considering rip-off strength and residual stress of steel bars and concrete in different status of damages is developed to predict the flexural behavior of CFS strengthened beams. Rip-off strength equation is obtained by modifying moment of inertia in the Robert's equation. And conformed developed nonlinear analysis program in variable of strengthening CFS amount and status of damages(initial, case1, case2, case3) and tension reinforcement ratio(0.2~1.0%).

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.243-254
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• 2002

This study investigates the structural behavior of cracked or uncracked RC columns retrofitted with CFS and evaluates the shear retrofit performance through experiment. Experimental works were conducted for sixth specimens varied in the adhesion method of CFS, the ratio of shear reinforcement bar, and the existence of crack before retrofitting. Throughout cyclic test, the strength, stiffness, failure modes, and ductility are discussed. The test results show that the retrofitting method with CFS improve the shear strength and ductility. The crack width below 2mm, occurred before retrofitting, didn't reduce the shear strengthening effect.

• 한국강구조학회 논문집
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• 제21권3호
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• pp.311-320
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• 2009

본 연구에서는 기존 각형 CFT기둥 실험체와 탄소섬유쉬트로 추가구속된 각형 CFT기둥 실험체의 단조압축거동 및 압축내력평가에 관한 실험을 수행하였다. 실험변수는 탄소섬유쉬트 보강겹수와 폭-두께비이며, 실험변수에 따라 총 9개의 실험체를 제작하여 단조압축실험을 수행하였다. 실험을 통하여 기존 CFT 실험체와 탄소섬유쉬트로 구속된 CFT 실험체의 파괴거동, 하중-축변위 곡선, 최대내력, 변형성능을 비교한다. 끝으로 탄소섬유쉬트의 추가구속은 기둥의 국부좌굴을 지연시켰으며 이로 인해 실험체의 최대내력이 상승한 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.203-211
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• 1999

This study is to examine the feasibility of carbon fiber sheet(CFS), a kind of fiber reinforced plastic(FRP), for a repair and reinforcement of R/C beams. The flexural strength of R/C beams, that were preloaded and then the cracks were repaired, maintains that of the uncracked R/C beams. The flexural strength of R/C beams increases with the reinforcement of CFS. In order to practically apply the repair and reinforcement method, further research is needed for the distribution, amount, and bond of CFS. In this study, an experiment was conducted for R/C beams reinforced with CFS, for various wrapping method and amounts of CFS. Experimental results showed the wrapping method increasing the bond area and amount of CFS layer caused the increase in the strength of the beams. It is found that the strength of CFS should be used as 70% of the maximum strength in retrofitting reinforced concrete beams in evaluating flexural capacity on the basis of ultimate strength design method.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.605-610
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• 2002

The purpose of this study is to develop an analytic model which can describe the behavior or concrete compressive member strengthened by CFS(Carbon Fiber Sheet) with various cross-sectional shapes such as circular. square, and octagonal and various laminate angles. The failure criterion of laminated CFS is based on Tsai-Wu failure criterion. The stress strain model of confined concrete compressive member is based on an equation proposed by Mander. The effective lateral confining pressure is considered and modified according to various cross-sectional shapes. Octagonal cross-section shows the best results in the aspect of ductility, while circular does in compressive strengthening effects. In addition, [0/0/0/0] laminate in which the direction of fiber is parallel to the direction of principal stress shows the superior strength and ductility than other laminates. The analytic results show that strength and ductility of the analytic model depend on the cross-sectional shapes as well as the laminate angles.