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Bond Properties of GFRP Rebar with Cover Thickness and Volume Fraction of Steel Fiber

강섬유 혼입률과 피복두께에 따른 GFRP 보강근의 부착특성

  • Choi, Yun-Chul (Dept. of Building Services Engineering & Fire Protection System, Chungwoon University)
  • 최윤철 (청운대학교 건축설비소방학과)
  • Received : 2012.10.04
  • Accepted : 2012.11.30
  • Published : 2012.12.31

Abstract

The purpose of this study is to investigate bond properties of GFRP used in SFRC (Steel fiber reinforced concrete) and normal concrete. The experimental variables were rebar diameter (D13, D16), steel fiber volume fraction (0~2%) and cover thickness ($1.5d_b$, $5.4d_b$). The experimental results showed a different failure mode depending on the cover thickness. Through the tested specimens, splitting failure occurred for the specimens with small cover thickness and pull out failure occurred in the specimens with large cover thickness. Introduction of steel fiber caused the specimens to have more ductile behavior of bond stresss-lip after peak stress, but they did not increase the bond strength significantly. These failure modes were shown in both steel reinforcement and GFRP. However, from the difference of micro structure of bond failure mechanism between steel rebar and GFRP rebar, more ductile behavior was observed in GFRP-specimens after maximum bond strength was reached.

이 연구는 강섬유 혼입률에 따른 피복두께와 GFRP 보강근의 부착특성을 부착응력-미끌림 관계를 통하여 평가하였다. 실험변수로는 강섬유 혼입률을 0%, 1%, 2%로 하였고 피복두께는 보강근 직경($d_b$)의 $1.5d_b$$5.4d_b$로 하였다. GFRP 보강근의 직경은 D13과 D16 두 가지를 사용하였으며, 비교실험을 위하여 이형철근을 사용하였다. 실험 결과 피복두께에 따 상이한 파괴형태를 취했으며, 작은 피복두께를 갖는 $1.5d_b$의 경우 쪼갬파괴 형태를 취했고 충분한 피복두께인 $5.4d_b$를 갖는 경우 뽑힘파괴 형태를 취했다. 이에 강섬유 혼입률을 증가시켰음에도 파괴형태에는 영향이 없었다. 그러나 강섬유 혼입률의 증가에 따라 최대부착응력 도달 후 급작스런 부착응력 감소폭이 감소하였다. 또한, 작은 피복두께를 갖는 경우 최대부착응력에 도달 전에 파괴되면서 강섬유 혼입률에 따른 부착응력의 차이가 거의 없었지만, 충분한 피복두께를 갖는 경우에는 최대부착응력에 도달 하면서 강섬유 혼입률 증가에 따라 부착응력이 증가하였다. 이는 강섬유의 가교작용으로 인해 콘크리트 내부의 미소균열 및 쪼개짐 균열의 성장을 억제하였기 때문으로 판단되었다.

Keywords

References

  1. Abdalla, H. A., "Evaluation of Deflection in Concrete Members Reinforced with Fiber Reinforced Polymer (FRP) Bars," Composite Structures, Vol. 56, Issue 1, 2002, pp. 63-71. https://doi.org/10.1016/S0263-8223(01)00188-X
  2. Choi, Y. C., Park, K. S., Choi, C. S., and Choi, H. K., "Bond Properties of GFRP Rebar in Fiber Reinforced Concrete (Engineered Cementitious Composite)," Journal of the Korea Concrete Institute, Vol. 23, No. 6, 2011, pp. 809-815. (doi: http://dx.doi.org/10.4334/JKCI.2011.23.6.809).
  3. Ha, S. S. and Yoon, J. S., "Comparison of Development Length Equation of Bottom and Top GFRP Bars with Splitting Failure," Journal of the Korea Institute of Building Construction, Vol. 9, No. 6, 2009, pp. 141-149. https://doi.org/10.5345/JKIC.2009.9.6.141
  4. Park, C. G., Won, J. P., and Kang, J. W., "Recommendations of Environmental Reduction Factor of FRP Rebar for Durability Design of Concrete Structure," Journal of the Korea Concrete Institute, Vol. 16, No. 4, 2004, pp. 529-539. https://doi.org/10.4334/JKCI.2004.16.4.529
  5. Haddad, R. H. and Abendeh, R. M., "Effect of Thermal Cycling on Bond between Reinforcement and Fiber Reinforced Concrete," Cement and Concrete Composites, Vol. 26, Issue 6, 2004, pp. 743-752. https://doi.org/10.1016/S0958-9465(03)00083-0
  6. Lee, J. Y., Yi, C. K., Kim, T. Y., Park, J. S., and Park, Y. H., "Bond Failure Surface of Glass Fiber Reinforced Polymer Bars," Journal of the Korea Concrete Institute, Vol. 20, No. 3, 2008, pp. 383-391. https://doi.org/10.4334/JKCI.2008.20.3.383
  7. Won, J. P., Park, C. G., Kim, H. H., and Lee, S. W., "Bond Properties of GFRP Rebar and High Strength Concrete with Steel Fiber Reinforcements," Journal of the Korea Society of Civil Engineers, Vol. 27, No. 2, 2007, pp. 265-270.
  8. Kang, Y. J., "A Study on Bond Behavior of GFRP Rebars Embedded in Fiber Reinforced Concrete," Journal of the SungKyunKwan University, 2012, pp. 1-64.
  9. Park, J. S., You, Y. J., Park, Y. H., and Kim, K. H., "An Experimental Study on the Bond Characteristics of GFRP Rebars with Bond Length," Journal of the Korea Society of Civil Engineers, Vol. 10, No. 10, 2007, pp. 2326-2329.
  10. Ha, S. S. and Choi, D. U., "Bond Characteristics of GFRP Bars with Small Cover Thickness," Journal of the HanKyong National University, 2007, pp. 39-48.
  11. Park, J. S., "Flexural Bonding Characteristics of Embedded Length of FRP rod Types," Journal of the HanYang University, 2010, pp. 1-58.
  12. Xial, J. and Falkner, H., "Bond Behavior between Recycled Aggregate Concrete and Steel Rebars," Construction and Building Materials, Vol. 21, Issue 2, 2007, pp. 395-401. https://doi.org/10.1016/j.conbuildmat.2005.08.008
  13. Tepfers, R., "Cracking of Concrete Cover along Anchored Deformed Reinforcing Bars," Magazine of Concrete Research, Vol. 31, No. 106, 1979, pp. 3-12. https://doi.org/10.1680/macr.1979.31.106.3
  14. Naaman, A. E. and Reinhardt, H. W., "Characterization of High Performance Fiber Reinforced Cement Composites," Proceeding of Second International Symposium on High Performance Fiber Reinforced Cementitious Composites, 1996, pp. 1-24.