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초고성능 섬유보강 콘크리트(UHPFRC)의 재료 특성 및 예측모델 2 : 구속 수축 특성 평가 및 구속도 예측
류두열,박정준,김성욱,윤영수 대한토목학회 2012 대한토목학회논문집 A Vol.32 No.5A
본 연구에서는 초고성능 섬유보강 콘크리트(Ultra High Performance Fiber Reinforced Concrete, UHPFRC)의 구속 상태에서의 수축 거동을 평가하고자 국내·외에서 가장 보편적으로 사용되는 링-테스트(ring-test)를 이용하여 구속 수축 실험을 수행하였다. 특히, 다양한 구속도에서의 수축 거동을 평가하기 위하여 내부 강재 링의 두께와 내부 반경을 달리하여 실험을 수행하였으며, 자유 수축과 인장강도 실험을 수반하여 구속도 및 응력 이완, 수축 균열 가능성 등을 복합적으로 평가하였다. 실험 결과 내부 링의 두께가 증가할수록 내부 링의 평균 변형률과 잔류 인장응력 감소하였으며, 반면에 구속도는 증가하는 경향을 보였다. 내부 링의 반경에 따라서는 변형률 및 잔류 인장응력, 구속도의 차이가 거의 없는 것으로 나타났다. 모든 시험체에서 잔류 인장응력이 인장강도에 비해 작은 것으로 나타났으며, 수축 균열은 발생하지 않았다. 지속적으로 작용하는 계면 구속 하중에 의해 탄성 수축 응력의 약 39~65%가 이완되는 것으로 나타났으며, 최대 이완 응력은 내부 링의 두께가 두꺼울수록 증가하는 것으로 나타났다. 마지막으로 본 연구에서는 비선형 회귀분석을 수행하여 재령에 따라 변하는 구속도를 예측하였으며, 실험 결과와 잘 일치하는 것으로 나타났다. In this study, to evaluate the shrinkage behavior of ultra high performance fiber reinforced concrete UHPFRC under restrained condition, restrained shrinkage test was performed according to ring-test mostly used at home and abroad. Ring-test was performed with the various thicknesses and radii of inner steel ring to give different degree of restraint. Free shrinkage and tensile tests were carried out simultaneously to estimate the degree of restraint, stress relaxation, and shrinkage cracking potential. Test results indicated that the average steel strain and residual tensile stress were reduced as the thicker inner steel ring was used, whereas degree of restraint was increased. The steel strain, residual tensile stress and degree of restraint were hardly affected by the size of radius of inner ring. In the case of all ring specimens, shrinkage crack did not occur because the residual tensile stress was lower than the tensile strength. About 39~65% of the elastic shrinkage stress was relaxed by the sustained interface pressure, and the maximum relaxed stress was increased as the thicker inner ring was applied. Finally, the degree of restraint with age was predicted by performing non-linear regression, and it was in good agreement with the test results.
황의철 ( Hwang Eui-chul ),김규용 ( Kim Guy-yong ),이상규 ( Lee Sang-kyu ),손민재 ( Son Min-jae ),백재욱 ( Baek Jae-wook ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2018 한국건축시공학회 학술발표대회 논문집 Vol.18 No.2
In this study, surface spalling and explosive spalling of ring-type ultra-high strength concrete under rapid heating and slow heating were investigated. In rapid heating, the internal temperature difference of the concrete is large, so that continuous surface spalling occurs. However, in slow heating, the difference in the internal temperature of the concrete is small, resulting in explosive spalling at a time. Since the heating condition has a great influence on the internal temperature of the concrete, it is necessary to consider the spalling of the concrete under various heating conditions.
링형 강관으로 구속된 고강도콘크리트의 수증기 압력과 폭렬 특성
백재욱,김규용,남정수,황의철,최경철,윤민호 한국콘크리트학회 2018 콘크리트학회논문집 Vol.30 No.6
In this study, spalling properties, internal temperature, water vapor pressure, and restrained stress of 40, 60, 80, and 100 MPa concrete were evaluated using ring-type restrained concrete specimen. Also, the effect of water vapor pressure and thermal stress on the spalling of concrete according to compressive strength was investigated. As a result, spalling was found to occur in concrete of 80 MPa or higher. This is because the higher the compressive strength of the concrete was, the greater the water vapor pressure that was generated in the independent pores during the heating. Similarly, the higher the compressive strength was, the greater was the thermal stress. As a result, it was confirmed that the restrained stress became larger in proportion to the expansion stresses, such as water vapor pressure and thermal stress. Therefore, it is considered that these results are valid for evaluation of the spalling properties of concrete according to the compressive strength using ring-type restrained concrete specimens.
고온에 노출된 링형 강관 구속 콘크리트의 폭렬 및 초음파투과시간
황의철 ( Hwang Eui-chul ),김규용 ( Kim Guy-yong ),이상규 ( Lee Sang-kyu ),손민재 ( Son Min-jae ),편수정 ( Pyeon Su-jeong ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2019 한국건축시공학회 학술발표대회 논문집 Vol.19 No.1
In this study, the spalling and ultrasonic pulse transmission time of concrete were investigated according to compressive strength during heating. As a result, the higher the compressive strength of the concrete, the more the explosion occurs, which affects the cross-sectional loss and the spalling fragment size. Also, ultrasonic pulse transmission time was found to be strongly influenced by the section loss of concrete.
황의철 ( Hwang Eui-chul ),김규용 ( Kim Guy-yong ),손민재 ( Son Min-jae ),서동균 ( Suh Dong-kyun ),이예찬 ( Lee Yae-chan ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2021 한국건축시공학회 학술발표대회 논문집 Vol.21 No.1
This study evaluated the vapor pressure and thermal stress of high-strength concrete according to spalling type. As a result, it was confirmed that the internal temperature gradient of the concrete varies depending on the heating rate, and the vapor pressure and thermal stress of the concrete are the main factors of spalling. In addition, it was confirmed that spalling type varies depending on the vapor pressure and thermal stress of the concrete.