Journal of the Korean Recycled Construction Resources Institute (한국건설순환자원학회논문집)

Korean Recycled Construction Resources Institute (한국건설순환자원학회)
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A Stress Transfer Length of Pre-tensioned Members Using Ultra High Performance Concrete

초고성능 콘크리트 프리텐션부재의 응력전달길이

  • Received : 2018.11.12
  • Accepted : 2018.11.28
  • Published : 2018.12.30
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Abstract

The prestressing force introduced to the tendon in pretensioned concrete members is transferred by direct bond between tendon and concrete, which requires a proper estimation of stress transfer length. The use of pretensiond and/or precast members with UHPC (Ultra High Performance Concrete) may give many advantages in quality control. This paper presents an experiment to estimate the stress transfer length of UHPC for various compressive strength levels of UHPC, cover depths, diameters of tendons and tensioning forces. According to the result of this experiment, the stress transfer length of UHPC member is much reduced comparing that of normal strength concrete. The reduction in stress transfer length of UHPC may come from the high bond strength capacity of UHPC. The transfer lengths obtained from this experiment are compared to those in current design code and a new formula is proposed.

프리텐션 콘크리트 부재에서 긴장재에 도입된 프리스트레싱힘은 긴장재와 콘크리트의 직접 부착에 의하여 콘크리트에 전달되므로 응력전달길이를 합리적으로 산정하는 것이 중요하다. 프리텐션부재 또는 프리캐스트 부재에 UHPC를 사용하는 경우 품질관리 측면에서 많은 장점이 있다. 따라서, 이 논문은 초고성능 콘크리트를 사용한 프리텐션 부재에 있어서 PS 강연선의 응력전달길이를 구하기 위하여 초고성능 콘크리트의 압축강도, 피복두께, 긴장재의 지름 및 긴장력을 변수로 하여 실험을 진행하고 그 결과를 분석한 내용을 정리한 것이다. 실험 결과에 따르면 초고성능 콘크리트를 사용한 경우 일반 콘크리트에 비하여 응력 전달길이가 크게 감소하였으며, 압축강도 수준이 증가할수록 응력전달길이가 감소하는 것을 확인할 수 있었다. 이는 초고성능 콘크리트의 높은 부착강도에서 비롯되는 것으로 판단된다. 또한, 실험결과와 기존 설계기준의 응력전달길이 산정식을 비교하고, 초고성능 콘크리트 프리텐션 부재의 응력전달길이를 산정할 수 있는 새로운 공식을 제안하였다.

Keywords

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Fig. 1. Test specimens(unit : mm)

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Fig. 2. Fabrication of specimens

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Fig. 3. Steam curing

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Fig. 4. Concrete strain gauge arrangement(unit : mm)

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Fig. 5. PS strand strain gauge arrangement

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Fig. 6. Stains measured along the specimens(180MPa UHPC)

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Fig. 7. Stains measured along the specimens(120MPa UHPC)

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Fig. 8. Comparison of transfer length with ACI

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Fig. 9. Comparison of transfer length with AASHTO LRFD

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Fig. 10. Comparison of transfer length with Eurocode 2

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Fig. 11. A Regression Analysis on 120MPa and 180MPa UHPC Experiment Result

Table 1. UHPC mix proportioning

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Table 2. Stress transfer length measured from cut end(mm)

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Table 3. Stress transfer length measured from dead end(mm)

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References

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