• Title/Summary/Keyword: carbon FRP sheet strengthening

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Structural Performance of Reinforced Concrete Beams Strengthened with Sprayed Fiber Reinforced Polymers (Sprayed FRP로 보강된 철근콘크리트 보의 보강성능에 관한 연구)

  • Lee, Kang-Seok;Son, Young-Seon;Lee, Moon-Sung
    • Journal of the Korea Concrete Institute
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    • v.19 no.4
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    • pp.421-431
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    • 2007
  • The main purpose of this study is to develop a sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing one of the carbon or glass chopped fibers and one of the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of the sprayed FRP, this study carried out tensile tests of the material specimens, which were changed with the combinations of various variables including the length of chopped fiber and the mixture ratio of chopped fiber and resin. These variables were set to have the equal material strength, compared with that of one layer of the FRP sheet. As a result, the optimal length of glass and carbon chopped fibers was fumed out to be 38 mm, and the optimal mixture ratio between chopped fiber and resin was also turned out to be 1 : 2 from each variable. And also, the thickness of the sprayed FRP to have the equal strength to one layer of the FRP sheet was finally calculated. In is study, a series of experiments were carried out to evaluate the strengthening effects of flexural beams, shear beams and damaged beams strengthened with the sprayed FRP method, respectively. The results revealed that the strengthening effects of the flexural and shear specimens were reasonably similar to those of the FRP sheet, and the developed Sprayed FRP technique is able to be used as a strengthening scheme of existing RC building.

Repair and Strengthening Methods for Concrete Structures using Sprayed Fiber Reinforced Polymers - Material Property of Sprayed FRP - (Sprayed FRP 공법에 의한 콘크리트 구조물의 보수.보강법 개발에 관한 연구 - Sprayed FRP를 구성하는 재료특성에 관한 연구 -)

  • Lee, Li-Hyung;Lee, Kang-Seok;Son, Young-Sun;Byeon, In-Hee;Lim, Byung-Ho;Na, Jung-Min
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.141-144
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    • 2006
  • The main purpose of this study is to develop a Sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing carbon or glass shot fibers and the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the Sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of Sprayed FRP, this study carried out tensile tests of the material specimens which are changed with the combinations of various variables such as the length of shot fiber and mixture ratio of shot fiber and resin. These variables are set to have the material strength equal to one layer of the FRP sheet. As a result, the optimal length of glass and carbon shot fibers were derived into 3.8cm, and the optimal mixture ratio was also deriver into 1:2 from each variable. And also, the thickness of Sprayed FRP to have the strength equal to one layer of FRP sheet was finally calculated.

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A Comparative Study on the Shear-Strengthening Effect of RC Beams Strengthened by FRP (FRP로 보강된 RC보의 전단보강효과 비교연구)

  • 심종성;김규선
    • Magazine of the Korea Concrete Institute
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    • v.10 no.4
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    • pp.101-111
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    • 1998
  • This study presents test results of RC beams strengthened by carbon fiber sheet(CFS), carbon fiber reinforced plastics(CFRP) or glass fiber reinforced plastics(GFRP) for increasing shear resistance. Nineteen specimens were tested, and the test was performed with different parameters including the type of strengthening materials(CFS, GFRP, CFRP), shear-strengthening methods(wing type, jacket type, strip type), strip-spacing, strengthening direction of FRP. The test results show that shear-damaged RC beams strengthened by FRP(CFS, GFRP, CFRP) have more improved the shear capacity. The mathematical model based on plastic theory was also developed to predict shear strength of shear-damaged RC beams strengthened by FRP. The predictions using the mathematical model. are agreed with the observations from the observed shear strengths for 19 test beams.

Repair and Strengthening Methods for Concrete Structures using Sprayed Fiber Reinforced Polymers - Strengthening Performance of Reinforced Concrete Beams - (Sprayed FRP 공법에 의한 콘크리트 구조물의 보수.보강법 개발에 관한 연구 - 철근콘크리트 보의 보강성능 평가 -)

  • Lee, Kang-Seok;Son, Young-Sun;Byeon, In-Hee;Lee, Moon-Sung;Na, Jung-Min;Lee, Li-Hyung
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.133-136
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    • 2006
  • The main purpose of this study is to develop a Sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing carbon or glass shot fibers and the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the Sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In this study, a series of experiments are carried out to evaluate the strengthening effects of the flexural and shear concret beams strengthened with the Sprayed FRP method. The results revealed that the strengthening effects of the flexural and shear specimens are similar, compared to those of the FRP sheet.

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Strengthening Performance of RC Beams Exposed to Freezing and Thawing Cycles after Strengthening in Shear with CFRP Sheet (CFRP 쉬트로 전단보강후 동결융해에 노출된 철근콘크리트 보의 보강성능)

  • Yun, Hyun-Do;Kim, Sun-Woo;Kim, Yun-Su;Lee, Min-Jung;Seo, Soo-Yeon;Choi, Ki-Bong
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.161-164
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    • 2008
  • In recent years, carbon fiber-reinforced polymer (CFRP) has been widely used for repairing and/or strengthening structural elements in concrete. Not enough test data, however, are available to predict the long-term performance of the repaired and improved structures exposed to weathering. The objective of this research is to study the effect of freeze-thaw cycling on the behavior of reinforced concrete (RC) beams strengthened in shear with carbon fiber sheet. Six small-scale RC beams (100mm${\times]$100mm${\times]$400mm) were strengthened with CFRP in shear, subjected to up to 400 cycles freeze-thawing from -17${\sim}4^{\circ}C$, and tested to failure in four-point bending. Test result, there was no significant damage to carbon fiber sheet strengthened concrete beams had been suffered 30 cycles of freeze-thawing, and more over 60 cycles of freezing-thawing brought about a reduction in resistance of only 25% of the initial level.

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The Flexural Strengthening Effect of I-Shape PFRP Member Using Carbon Fiber Sheet (탄소섬유시트를 이용한 I형 PFRP 부재의 휨보강 효과)

  • Lee, Young-Geun;Kim, Sun-Hee;Lee, Kang-Yeon;Yoon, Soon-Jong
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.4 no.2
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    • pp.1-7
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    • 2013
  • In recent years, fiber reinforced polymer plastic composites are readily available in the construction industry. Fiber reinforced polymer composite has many advantages such as high specific strength and high specific stiffness, high corrosion resistance, light-weight, magnetic transparency, etc. In this paper, we present the result of investigation pertaining to the flexural behavior of flange strengthened I-shape pultruded fiber reinforced polymer plastic (PFRP) member using carbon fiber sheet (CFRP sheet). Test variable is consisted of the number of layers of strengthening CFRP sheet from 0 to 3. From the experimental results, flexural strengthening effect of flange strengthened I-shape PFRP member using CFRP sheet is evaluated and it was found that 2 layers of strengthening CFRP sheet are appropriate considering efficiency and workability.

Impact Resistance Evaluation of RC Beams Strengthened with Carbon FRP Sheet and Steel Fiber (CFRP 시트 및 강섬유로 보강된 RC 보의 충격저항 성능 평가)

  • Cho, Seong-Hun;Min, Kyung-Hwan;Kim, Yun-Ji;Yoon, Young-Soo
    • Journal of the Korea Concrete Institute
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    • v.22 no.5
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    • pp.719-725
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    • 2010
  • The analysis and experimental program of reinforced concrete (RC) structures for resistance against such extreme loads as earthquake, blast, and impact have been carried by many researchers and designers. Under the extreme loads, a large amount of energy is suddenly exerted to the structure, hence if the structure fails to absorb the impact energy, catastrophic collapse may occur. To prevent catastrophic collapse of structures, reinforced concrete must have adeguate toughness or it needs to be strengthened. The FRP strengthening method and SFRC are studied widely in resistance of impact load because of their high energy absorption capacity. In this study, drop weight impact tests were implemented to evaluate the impact resistance of SFRC and FRP strengthened RC beam while the total steel fiber volume fractions was fixed at 0.75% carbon FRP flexural strengthened RC beams. Futhermore, to prevent the shear-plug cracks when the impact load strikes the beams, additional FRP shear strengthening method are applied. The experimental, results showed that the FRP strengthened RC SFRC beams has high resistance of shear-plug cracks and crack width and SFRC has high resistance of concrete spalling failure compared to normal RC beams. The FRP flexural and shear strengthening RC beams has weakness in the spalling failure because the impact load concentrated the concrete face which is not strengthened with FRP sheets.

Optimum Combination of Carbon and Glass Fiber Composite to Obtain the Hybrid Effect (하이브리드 효과를 주는 탄소섬유와 유리섬유의 최적 조합비)

  • Song, Hyung-Soo;Min, Chang-Shik
    • Journal of the Korea Concrete Institute
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    • v.23 no.4
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    • pp.405-411
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    • 2011
  • Using combinations of carbon and glass fiber composites normally used for strengthening of concrete structures, the hybrid effect from strengthening concrete structures using the composite is studied. To produce the hybrid effects, the specimens were made with optimum proportions of carbon fibers with glass fibers. Then, direct tensile tests were conducted on the hybrid FRP (fiber reinforced polymer) specimens. Unlike the woven fiber sheet currently used in construction sites, the FRP specimens have to be directly combined with the fibers, which make the work very complicated. Therefore, direct tensile test specimens manufacturing method based on the combination of high-tension carbon fibers and E-type glass fibers was proposed and the effects of hybridization is studied through the direct tensile test. By comparing the ductility index, the modulus of elasticity, and the stress-strain curves of the specimens, the most optimum glass to carbon fiber combination ratio for the hybrid FRP was found to be 9 to 1 with ductile K-type epoxy. The study results are discussed in detail in the paper.

An Experimental Study on the Strengthening Effect of RC Beam subjected to Repeated Loading during CFS Strengthening Process (탄소섬유 보강 중에 반복하중을 받은 RC보의 보강효과에 관한 실험적 연구)

  • Jang, Hee-Suk;Kim, Hee-Sung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.1
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    • pp.183-189
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    • 2006
  • When RC structures are repaired or strengthened using FRP, it is required to cure for some Period under certain air temperature and then it is hopeful to avoid detrimental action caused by external vibration sources during that period. Therefore, an effect of repeated loading during Carbon Fiber Sheet(CFS) strengthening Process on the strengthening efficiency is studied through an experiment for a number of RC beams. Experimental results showed that the curing time of 24 hours without any repeated loading after CFS attachment were recommended for 1 ply strengthening, and 12 hours for 2 plies strengthening.

Effect of Bond Length and Web Anchorage on Flexural Strength in RC Beams Strengthened with CFRP Plate (부착길이와 복부정착이 CFRP판으로 보강된 RC 보의 휨 보강효과에 미치는 영향)

  • 박상렬
    • Journal of the Korea Concrete Institute
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    • v.14 no.5
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    • pp.645-652
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    • 2002
  • This paper presents the flexural behavior and strengthening effect of reinforced concrete beams bonded with carbon FRP plate. Parameters involved in this experimental study were plate bond length and sheet web anchorage length. Test beams were strengthened with FRP plate on the soffit and anchored with FRP sheet on the web. In general, strengthened beams with no web anchorage were failed by concrete cover failure along the longitudinal reinforcement. On the other hand, strengthened beams with web anchorage were finally failed by delamination shear failure within concrete after breaking of CFRP sheet wrapping around web. The ultimate load and deflection of strengthened beams increased with an increased bond length of FRP plate. Also, the ultimate load and deflection increased with an increased anchorage length of FRP sheet. Particularly, the strengthened beams with web anchorage maintained high ultimate load resisting capacity until very large deflection. The shape of strain distribution of CFRP plate along beam was very similar to that of bending moment diagram. Therefore, an assumption of constant shear stress in shear span could be possible in the analysis of delamination shear stress of concrete. In the case of full bond length, the ultimate resisting shear stress provided by concrete and FRP sheet Increased with an increase of web anchorage length. In the resisting shear force, a portion of the shear force was provided by FRP anchorage sheet.