Journal of the Korea Concrete Institute (콘크리트학회논문집)

Korea Concrete Institute (한국콘크리트학회)
권호 표지
DOI QR코드

DOI QR Code

Ultimate Stress of Unbonded Tendons in Post-Tensioned Flexural Members

포스트텐션 휨부재에서 비부착긴장재의 극한응력

  • Lee, Deuck-Hang (School of Architecture and Architectural Engineering, University of Seoul) ;
  • Kim, Kang-Su (School of Architecture and Architectural Engineering, University of Seoul)
  • Published : 2009.08.31
Download PDF
⟨ Previous Next ⟩

Abstract

It is quite difficult to predict the flexural strength of post-tensioned members with unbonded tendons (unbonded posttensioned members, UPT members) because of debonding behavior between concrete and prestressing tendons, which is different from that with bonded tendons. Despite many previous researches, our understanding on the flexural strength of UPT members is still insufficient, and thus, national codes use different methods to calculate the strength, which quite often give very different results. Therefore, this paper reviews various existing methods, and aims at proposing an improved rational strength model for UPT flexural members having better accuracy. Additionally, a database containing a large number of test data on UPT flexural members has been established and used for verification of the proposed flexural strength model. The analysis results show that the proposed method provides much better accuracy than many existing methods including the rigid-body model that utilizes the assumption of concentrated deformation and plastic hinge length, and that it also gives proper consideration on the effects of primary parameters such as reinforcement ratio, loading pattern, concrete strength, etc. Especially, the proposed method also well predicts the ultimate stress of unbonded tendons of over-reinforced members, which are often possible in construction fields, and high strength concrete members.

비부착 긴장재를 적용한 프리스트레스트 휨부재는 부착방식과 다르게 콘크리트와 긴장재의 비부착 거동 때 문에 휨강도의 정확한 예측이 쉽지 않다. 이에 대한 많은 연구들이 진행되었지만 비부착 긴장재를 적용한 부재의 휨강 도에 대한 이해는 여전히 부족하여, 각국의 기준은 매우 다르고 동일한 부재에 대하여 서로 다른 예측값을 주는 경우 가 많다. 따라서, 본 논문은 기존 제안식들을 고찰하고, 이를 개선하여 보다 합리적면서 향상된 정확도를 가질 수 있는 비부착긴장재의 극한응력예측식을 제안하고자 하였다. 또한, 비부착긴장재를 적용한 부재의 휨강도에 대한 기존의 실험 결과를 광범위하게 수집하여 데이터베이스를 구축하고, 이를 활용하여 제안모델의 정확성을 검증하고자 하였다. 변형의 집중을 가정하고 소성힌지 길이를 이용한 강체거동모델 등 기존의 제안식들에 비하여 본 논문에서 제안한 극한응력예 측식은 매우 뛰어난 정확도를 보였으며, 철근보강비, 재하형태, 콘크리트의 강도 등 주요 인자들의 영향을 매우 적절하 게 반영하는 것으로 나타났다. 특히, 보수·보강시 발생할 수 있는 과보강 상황 및 고강도콘크리트 부재에 대해서도 매 우 정확한 비부착긴장재의 극한응력을 제공하였다.

Keywords

References

  1. Collins, M. P. and Mitchell, D., Prestressed Concrete Structure, Prentice Hill, 1991, 766 pp
  2. Warwaruk, J., Sozen, M. A., and Siess, C. P., “Investigation of Prestressed Concrete for Highway Bridges, Part.: Strength and Behavior in Flexure of Prestressed Beam,” Bulletin, No. 464, Enginnering Experiment Station, Universsity of Illinois, Urbana, Ill., 1962. 105 pp
  3. Janney, J. R., Hognestad, E., and Mchenry, D., “Ultimate Flexural Strength of Prestressed and Conventionally Reinforced Concrete Beam,” ACI Structural Journal, Title No. 52-37, 1956, pp. 601-620
  4. Du, G. and Tao, X., “Ultimate Stress of Unbonded Tendons in Partially Prestressed Concrete Beams,” PCI Journal, Vol. 30, No. 6, 1985, pp. 72-91 https://doi.org/10.15554/pcij.11011985.72.91
  5. Harajli, M. H. and Kanj, M. Y., “Ultimate Flexural Strength of Concrete Members Prestressed With Unbonded Tendons,” ACI Structural Journal, Vol. 88, No. 6, 1991, pp. 663-673
  6. Campbell, T. I. and Chouinard, K. L., “Influence of Nonprestressed Reinforcement on the Strength of Unbonded Partially Prestressed Concrete Member,” ACI Structural Journal, Vol. 88, No. 5, 1991, pp. 546-551
  7. Chakrabarti, P. R., “Ultimate Stress for Unbonded Post-Tensioning Tendons in Partially Prestressed Beam,” ACI Structural Journal, Vol. 92, No. 6, 1995, pp. 689-697
  8. 문정호, 임재형, 이창규, “비부착 프리스트레스트 보강재를 갖는 PSC부재의 변위와 프리스트레스트 보강재 응력의 상관관계 및 변수별 효과,” 콘크리트학회 논문집, 14권, 2호, 2002, pp. 171-179 https://doi.org/10.4334/JKCI.2002.14.2.171
  9. Ozkul, O., Nassif, H., Tanchan, P., and Harajli, M. H., “Rational Approach for Predicting Stress in Beams with Unbonded Tendons,” ACI Structural Journal, Vol. 105, No. 3, 2008, pp. 338-347
  10. Tam, A. and Pannell, F. N., “The Ultimate Moment Resistance of Unbonded Partially Prestressed Reinforced Concrete,” Magazine of Concrete Research, Vol. 28, No. 97, 1976, pp. 203-208 https://doi.org/10.1680/macr.1976.28.97.203
  11. Harajli, M. H., “Effect of Span-Depth Ratio on The Ultimate Steel Stress in Unbonded Prestressed Concrete Members,” ACI Structural Journal, Vol. 87, No. 3, 1990, pp. 305-312
  12. Harajli, M. H., “On the Stress in Unbonded Tendon at Ultimate: Critical Assessment and Proposed Change,” ACI Structural Journal, Vol. 103 No. 6, 2006, pp. 803-812
  13. Naaman, A. E. and Alkhairi, F. M., “Stress at Ultimate in Unbonded Post Tensionning Tendons-Part 1: Evaluation of the State-of-the-Art,” ACI Structural Journal, Vol. 88, No.5, 1991, pp. 641-651
  14. Naaman, A. E. and Alkhairi, F. M., “Stress at Ultimate in Unbonded Post Tensionning Tendons-Part 2: Proposed Methodology,” ACI Structural Journal, Vol. 88, No. 6, 1991, pp. 693-692
  15. Bondy, K. B., “Realistic Reqirements for Unbonded Post-Tensioning Tendons,” PCI Journal, 1970, pp. 50-59
  16. Lee, L. H., Moon, J. H., and Lim, J. H., “Proposed Methodology for Computing of Unbonded Tendon Stress at Flexural Failure,” ACI Structural Journal, Vol. 96, No. 6, 1999, pp. 1040-1048
  17. Au, F. T. K. and Du, J. S., “Prediction of Ultimate Stress in Unbonded Tendons,” Magazine of Concrete Research, Vol. 56, No. 1, 2004, pp. 1-11 https://doi.org/10.1680/macr.2004.56.1.1
  18. Macgregor, R. J. G., Kregor, M. E., and Breen, J. E., “Strength and Ductility of Three Span Externally Post-Tensioned Segmental Box Girder Bridge Model,” Research Report No. 365-3F, Center for Transportation Research, The University of Texas, Austin, Texas, 1989, 299 pp
  19. Robert-Wollmann, C. L., Kregor, M. E., Rogosky, D. M., and Breen, J. E., “Stress in External Tendons at Ultimate,” ACI Structural Journal, Vol. 102, No. 2, 2005, pp. 206-213
  20. Bui, D. K. and Niwa, J., “Prediction of Loading-Induced Stress in Unbonded Tendons at Ultimate,” Doboku Gakkai Ronbunshu E, Vol. 62, No. 2, 2006, pp. 428-443 https://doi.org/10.2208/jsceje.62.428
  21. Allouche, E. N., Campbell, T. I., Green, M. F., and Soudki, K. A., “Tendon Stress in Continuous Unbonded Prestressed Concrete Members-Part 1 : Parametric Study,” PCI Journal, Vol. 44, No. 1, 1999, pp. 86-93
  22. Allouche, E. N., Campbell, T. I., Green, M. F., and Soudki, K. A., “Tendon Stress in Continuous Unbonded Prestressed Concrete Members - Part 2 :Review of Literature,” PCI Journal, Vol. 44, No. 1, 1999, pp. 60-73
  23. ACI Committee 318, “Building Code Requirements for Structural Concrete and Commentary (ACI 318M-05),” American Concrete Institute, Farmington Hills, 2005, 436 pp
  24. American Association of State Highway and Transportation Officials, “AASHTO LRFD Bridge Design Specifications,” Third Edition, AASHTO, Washington, DC, 2004, 1450 pp
  25. CAN3-A23.3-M94, “Design of Concrete Structure,” Canadian Standard Association, Rexdale, Ontario, 1994, 353 pp
  26. BSI 8110-85, “Section 4.3.7.3: Structural Use of Concrete,” British Standards Institution, London, 1985, 161 pp
  27. DIN 4227, “Part 6: Prestressed Concrete, Construction of Prestressed Concrete Member,” German Code, 1980, 365 pp
  28. NEN 3880, “Part H : Regulations for Concrete,” Dutch Code, 1984, Section 503.1.3.
  29. 한국콘크리트학회, 콘크리트구조설계기준해설, 한국콘크리트학회, 2007, 523 pp
  30. Mojtahedi, S. and Gamble, W. L., “Ultimate Steel Stresses in Unbonded Prestressed Concrete,” ASCE, Journal of Structural Division, Vol. 104, No. ST7, 1978, pp. 1159-1165