Proposal on the Prediction Equation of Ultimate stress of External Tendon for the Prestressed Concrete Beams with External Tendons

외부 PSC 보에서 외부강선의 극한 응력 예측식 제안

  • 유성원 (우석대학교 토목환경공학과) ;
  • 하헌재 (한국건설생활환경시험연구원)
  • Received : 2010.08.03
  • Accepted : 2010.10.12
  • Published : 2010.10.31

Abstract

Recently, the external prestressed concrete structures are increasingly being built. The mechanical behavior of prestressed concrete beams with unbonded tendon is different from that of normal bonded PSC beams in that the increment of tendon stress was derived by whole member behavior. By this reason, the ultimate stress of external tendon is smaller than that of bonded tendon or internal unbonded tendon. However, in the domestic and abroad code, the equation of ultimate stress of external tendon is not suggested yet, and the equation of ultimate stress of internal unbonded tendon is used instead of that of external tendon. Therefore, in this paper, after effective variables of ultimate stress of external tendon were analyzed, the analytical equation of ultimate stress of external tendon was proposed. And the reasonable coefficients were proposed by statistical work of test results of 25 beam with external tendon. Finally, the practical proposed equation of ultimate stress of external tendon was proposed with analytical and statistical model. The equation of ACI-318 and AASHTO 1994 were not matched with test results and had no correlations, and the proposed equation was well matched with test results. So the proposed equation in this paper will be a effective basis for the evaluation of external tendons in analysis and design.

Acknowledgement

Supported by : 우석대학교

References

  1. 오병환, 유성원, "외부 비부착 강선을 가진 PSC 교량의 휨거동 해석기법 및 해석 프로그램 개발", 대한토목학회논문집, 제19권, 제I-5호, pp. 761-771, 1999.9.
  2. 유성원, "외부 비부착 강선을 가진 프리스트레스트 콘크리트 부재의 극한 휨거동 해석", 서울대학교, 박사학위논문, 1999.
  3. 조윤구, "편향부와 강선구배 특성을 고려한 외부프리스트레스트 콘크리트 보의 휨거동에 관한 실험적 연구", 서울대학교, 박사학위논문, 2002.
  4. P. S. Rao, "Behavior of External PS Concrete Beams with Multiple deviators", ACI, Structural Journal, Vol. 93, No. 4, 1996.
  5. 홍성수, 유성원, 박승범, "비부착 PSC 보에서의슬립이 없는 강선의 극한 응력 예측에 관한 연구",대한토목학회논문집, 제28권, 제4A호, pp. 537-548, 2008.7.
  6. Mattok, A. H., and Yamazaki, J., and Katula, B., "Comparative Study of prestressed Concrete Beams, With and Without Bond", ACI Journal, Proceedings, Vol. 68, No. 2, February, pp. 116-125, 1971.
  7. Mojtahedi, S., and Gamble, W., "Ultimate Steel Stress in Unbonded Prestressed Concrete", J. of Structural Division, ASCE, Vol. 104, No. ST7, July, pp. 1159- 1165, 1978.
  8. 박상렬, 양철영, 김창훈, "CFRP 긴장재를 이용한외부 보강 철근콘크리트 보의 극한 휨강도 ", 한국콘크리트학회논문집, 제27권, 제5A호, pp. 671-679, 2007.10.
  9. Naaman, A. E. and Alkhairi, F. M., "Stress at Ultimate in Unbonded Post-Tensioning Tendons: Part 2 - Proposed Methodology", ACI, Structural Journal, Vol. 88, No. 6, 1991.
  10. 건설교통부, 도로교 설계기준, 1999.
  11. 건설교통부, 콘크리트 구조 설계기준, 1999.