Journal of the Korea Concrete Institute (콘크리트학회논문집)

Korea Concrete Institute (한국콘크리트학회)
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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 (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Min, Kyung-Hwan (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Kim, Yun-Ji (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Yoon, Young-Soo (School of Civil, Environmental and Architectural Engineering, Korea University)
  • 조성훈 (고려대학교 건축사회환경공학부) ;
  • 민경환 (고려대학교 건축사회환경공학부) ;
  • 김윤지 (고려대학교 건축사회환경공학부) ;
  • 윤영수 (고려대학교 건축사회환경공학부)
  • Received : 2010.05.26
  • Accepted : 2010.07.16
  • Published : 2010.10.31
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Abstract

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.

최근 콘크리트 구조물에 충격하중, 폭발하중 등 극한의 외력이 작용하는 경우가 빈번하게 발생하고 있다. 이 연구에서는 강섬유보강 RC보와 carbon FRP 시트를 이용하여 보강한 RC보를 이용하여 충격실험을 진행하였다. 강섬유보강 RC보의 경우 0.75%부피비로 강섬유를 혼입하였으며 carbon FRP 시트의 경우 에폭시 레진을 이용하여 보강을 한후 보 부재를 완성하였다. FRP 시트 보강은 부재의 하단을 휨 보강하였으며 충격하중이 부재에 작용할 때 발생하는 shear-plug 균열을 제어하기 위하여 충격하중이 가해지는 국부에 CFRP 전단보강을 실시하였다. 실험진행은 drop-weight test 방식으로 직접 기기를 만들어 실행하였다. 각각의 부재에 단계별로 충격하중을 가하여 실험을 진행하였으며 균열과 균열폭을 측정하였다. 실험결과 강섬유보강 RC보가 일반 RC보에 비하여 균열폭 및 shear-plug 균열제어 그리고 스폴링파괴에 더 높은 성능을 나타내었다. FRP로 부재의 하단을 휨 보강한 부재의 경우 균열의 제어에 어느정도 효과를 나타내고 있으나 충격하중이 가해질 시 콘크리트와 FRP 시트의 부착면에서 박리파괴가 빠르게 진행되었다. FRP 시트로 부재의 하단과 측면을 CFRP로 휨, 전단보강한 부재의 경우 shear-plug 균열제어에 가장 높은 저항성능을 보이고 있음을 확인할 수 있었다. 하지만 충격하중이 보강이 이루어지지 않은 부분에 작용할 경우 오히려 보강이 되지 않은 RC보에 비하여 콘크리트 스폴링 파괴에 더 취약함을 알 수 있었다.

Keywords

References

  1. 김영우, 민경환, 양준모, 윤영수, “하이브리드 PVA 섬유를 이용한 HPFRCC의 휨 및 충격 성능 평가,” 콘크리트학회 논문집, 21권, 6호, 2009, pp. 753-756. https://doi.org/10.4334/JKCI.2009.21.6.705
  2. 오병환, “철근콘크리트 벽체의 충격거동 및 충격해석연구,” 콘크리트학회 논문집, 4권, 2호, 1992, pp. 705-712.
  3. Saatci. S. and Vecchio, F. J., “Effects of Shear Mechanism on Impact Behavior of Reinforced concrete Beams,” ACI Structural Journal, Vol. 106 No. 1, 2009, pp. 78-86.
  4. Yankelevsky, D. Z., “Local Response of Concrete Slabs to Low Velocity Missile Impact,” International Journal of Impact Engineering, Vol. 19, No. 4, 1997, pp. 331-343. https://doi.org/10.1016/S0734-743X(96)00041-3
  5. Nataraja, M. C., Dhang, N., and Gupta, A. P., “Statistical Variations in Impact Resistance of Steel Fiber-Reinforced Concrete Subjected to Drop Weight Test,” Cement and Concrete Research, Vol. 29, No. 7, 1999, pp. 989-995. https://doi.org/10.1016/S0008-8846(99)00052-6
  6. Li. Q. M., Reid. S. R., Wen. H. M., and Telford. A. R., “Local Impact Effects of Hard Missiles on Concrete Targets,” International Journal of Impact Engineering, Vol. 32, Nos. 1-4, 2005, pp. 224-284. https://doi.org/10.1016/j.ijimpeng.2005.04.005
  7. Kishi, N. and Mikami, H., “Impact Behavior of Shear-Failure-Type RC Beams without Shear Rebar,” International Journal of Impact Engineering, Vol. 27, No. 9, 2002, pp. 955-968. https://doi.org/10.1016/S0734-743X(01)00149-X
  8. Ishai, O. and Shragai, A., “Effect of Impacts Loading on Damage and Residual Compressive Strength of CFRP Laminated Beams,” Composite Structures, Vol. 14, No. 4, 1990, pp. 319-337. https://doi.org/10.1016/0263-8223(90)90013-5
  9. Mindess, S., Chen, L., and Morgan, D. R., “Determination of the First-Crack Strength and Flexural Toughness of Steel Fiber-Reinforced Concrete,” Advanced Cement Based Materials, Vol. 1, 1994, pp. 201-208. https://doi.org/10.1016/1065-7355(94)90025-6

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