• Earthquakes and Structures
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• 제10권3호
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• pp.613-628
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• 2016

The effectiveness of the use of modern repair schemes for the seismic retrofit of existing RC structures were assessed on a comparative experimental study of carbon fiber-reinforced polymer (CFRP) strips and sheets for the repair of reinforced concrete members of RC frames, damaged because of cyclic loading. Two virgin, single - story, one - bay, 1/3 - scale frame specimens were tested under cyclic horizontal loading, up to a drift level of 4%. Then, virgin specimens, B and F, respectively, were repaired and retested in the same way. One, specimen RB, was repaired with epoxy injections and CFRP strips and one, specimen RF, was repaired with epoxy injections and CFRP sheets. The two specimens are used to examine the differences between the structural behavior of frames repaired using CFRP strips and frames repaired using CFRP sheets. Both qualitative and quantitative conclusions, based on the observed maximum loads, loading and reloading stiffness, hysteretic energy absorption and failure mechanisms are presented and compared. The repaired frames recovered their strength, stiffness and energy dissipated reasonably. The use of CFRP sheets was found more effective than CFRP strips, due to the proper anchorage.

• 비파괴검사학회지
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• 제23권2호
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• pp.133-139
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• 2003

노후 된 콘크리트 사회기반시설 구조물의 활용성 증대와 수명의 연장을 위하여 여러 가지의 보수보강 방법이 시행되어지고 있으나 최근에는 시공이 용이하고 보강효과가 좋은 탄소섬유시트를 활용하는 방법이 널리 쓰여지고 있다. 탄소 섬유로 보수보강을 할 경우 강도가 증진되고 강성이 향상되어 좋은 방법으로 알려져 있으나, 철근 콘크리트에 비해 연성이 떨어져 파괴 시 취성 파괴의 형태를 보일 수 있다, 그리고 보수보강된 구조물을 보강재로 인하여 크랙의 진전을 맨눈으로 확인하기가 어려워지게 된다. 따라서 구조물의 취약함을 드러내는 시기인 보수보강시 광섬유센서를 내장케 하여 취성파괴를 감시하고 구조물의 거동을 모니터링함으로써 안전한 구조물이 되도록 할 수 있다. 이를 위하여 본 논문에서는 광섬유센서를 이용하여 모재와 보강재의 구조거동을 분석하였으며, Peel out 효과라 불리는 계면 파괴현상을 효과적으로 자기진단 할 수 있음을 입증하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.573-578
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• 1999

The reinforced concrete slabs with epoxy-bonded AFRT sheets were experimentally investigated. Experimental data on strength, stiffness, steel strain, deflection and mode of failure of strengthened slabs were obtained, and comparisons between the different flexural reinforcing schemes and reinforced concrete slabs without AFRT sheets were made. The result generally indicate that the flexural strength, ductile behavior of strengthened slabs increased.

• 한국지진공학회논문집
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• 제11권1호
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• pp.37-43
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• 2007

탄소섬유관으로 구속된 원형 무근콘크리트 부재는 콘크리트에 효과적인 횡구속을 제공하며, 섬유의 우수한 역학적 성질로 인하여 기존의 철근을 대체할 수 있는 우수한 합성부재이다. 본 논문에서는 탄소섬유관으로 구속된 원형 무근콘크리트 보에 관한 실험 및 해석연구를 실시하였다. 실험연구에서 시험체는 두께 1.5mm(3장), 2.0mm(4장), 2.5mm(5장) 및 3.0mm(6장)를 변수로 하여 실험을 실시하였다. 구속된 콘크리트의 압축강도를 예측하는 식을 이용하여 본 연구에서는 탄소섬유 관으로 구속된 원형 무근 콘크리트 보의 휨성능을 예측하는 실험식을 제안하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제12권2호
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• pp.131-138
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• 2008

최근 지진, 노후화 등에 따라 손상된 많은 콘크리트 구조물을 보강하기 위하여 고강도이면서 가볍고 내구성이 뛰어난 특성을 가지고 있는 FRP(Fiber-reinforced polymer) 시트가 구미에서 뿐만 아니라 우리나라에서도 널리 사용되고 있으며 관련연구도 활발히 체계적으로 이루어지고 있다. 일반적으로 FRP 시트로 보강된 RC구조물은 지진, 교통, 온도 등에 의해 자주 반복하중을 받는다. 그러나 대부분의 연구가 일축 하중하에 이루어진 경우가 대부분이며 이러한 연구결과를 토대로 FRP의 부착특성을 확인하고 있으며 다양한 부착모델을 제안하고 있다. 이러한 관점에서 본 연구에서는 아라미드섬유, 탄소섬유, 폴리아세탈 섬유와 매수를 변수로 하여 총 18개의 시험체를 제작하고 최대부착강도, 최대변위, 변형률을 측정하고 그 결과에 근거하여 부착응력, 슬립을 계산하여 반복하중하의 FRP 시트와 콘크리트의 부착특성을 미시적으로 살펴보았다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.991-996
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• 2001

The strengthening of concrete structures in situ with externally bonded fiber sheets is increasingly being used for repair and rehabilitation of existing structures. Because fiber sheets is attractive for this application due to its good tensile strength, resistance to corrosion, and low weight. But, debonding failure may occur at the beam ends that fiber sheet bonded to the soffit of a beam. The method which can prevent debonding failure is suggested and proved its efficiency by using CPS experimental test. And this paper summarized the results of experimental studies concerning the end-anchorage system. Results show that the suggested method is faithful in strengthening with CFS.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.169-172
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• 2005

Recently the repair of damaged reinforced concrete members by the external bonding of fiber-reinforced polymer laminates has received considerable attention. This paper investigates the flexural behaviors of beam strengthened with Aramid fiber sheets(AFS), and attempts to evaluate the flexural strength of such RC beams by the use of nonlinear flexural analysis because the application of the KCI strength method to strengthened beam is somewhat limited and the failure strain of AFS is overestimated in particular cases.

• 펄프종이기술
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• 제34권2호
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• pp.61-66
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• 2002

This study was carried out to investigate sheet properties of Indian mallow hanji, made by different pulping methods such as alkali and sulfomethylated pulpings, and different stock compositions, various mixing ratios of bast fiber and woody core fibers. Effect of morphological properties of pulp stocks on the sheet formation and their optical properties were also evaluated using an image analyzer and confocal laser scanning microscope(CLSM). In addition, the effect of fiber distribution index(FDI), which was calculated based on the image in a z-direction of a sheet from CLSM, on the sheet properties of Indian mallow hanji was discussed. The proposed FDI had a good correlation with various properties of paper, such as apparent density, opacity, tear index, breaking length and zero-span tensile strength. Especially, sulfomethylated pulp sheets＇FDI was higher than alkali pulp sheets.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.519-524
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• 2007

Recently, Fiber sheets have been used for strengthening the deteriorated reinforced concrete RC slabs because of its resistant capacity of corrosion and repairing works. The purpose of this study is to carry out the experimental studies on thirteen kinds of RC slabs and to investigate the behavior of RC slabs form the experimental results. Test parameters are the strengthening material, the number of sheet layer and strengthening direction. The behavior of strengthened He: slabs is represented by crack load-deflection curves and maximum load. And the parametric study based on the nonlinear FEM analysis are performed and its results are discussed.

• International Journal of Concrete Structures and Materials
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• 제7권1호
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• pp.3-16
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• 2013

Strengthening concrete structures using FRP composites is a commonly considered technology in many practical situations. The success of the strengthening intervention largely depends on adequate bond between FRP sheets and the concrete substrate. In recent years, techniques to anchor FRP sheets in applications where sheets must develop strength in a short length have been proposed. One of these techniques includes use of FRP anchors embedded into the concrete substrate and forming part of the composite strengthening system. This paper presents the results of studies conducted recently at the University of Massachusetts Amherst to advance the understanding on the behavior of FRP anchored systems.