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Evaluation for Mechanical Properties of High Strength Concrete at High Temperature by Stressed Test and Unstressed Test

설계하중 사전재하 및 비재하방식에 의한 고강도콘크리트의 고온특성 평가

  • Kim, Gyu-Yong (Div. of Architectural Engineering, Chungnam National University) ;
  • Kim, Young-Sun (Div. of Architectural Engineering, Chungnam National University) ;
  • Lee, Tae-Gyu (Div. of Architectural Engineering, Chungnam National University) ;
  • Park, Chan-Kyu (Architectural Engineering & Technology Team, Samsung Corporation Co.) ;
  • Lee, Seung-Hoon (Architectural Engineering & Technology Team, Samsung Corporation Co.)
  • 김규용 (충남대학교 건축학부) ;
  • 김영선 (충남대학교 건축학부) ;
  • 이태규 (충남대학교 건축학부) ;
  • 박찬규 (삼성물산(주)건설부문 기술연구소) ;
  • 이승훈 (삼성물산(주)건설부문 기술연구소)
  • Published : 2008.10.31

Abstract

Recently, the effects of high temperature on compressive strength, elastic modulus and strain at peak stress of high strength concrete were experimentally investigated. The present study is aimed to study the effect of elevated temperatures ranging from 20 to 700 on the material mechanical properties of high strength concrete of 40, 60, 80 MPa grade. In this study, the types of test were the stressed test and stressed residual test that the specimens are subjected to a 25% of ultimate compressive strength at room temperature and sustained during heating and when target temperature is reached, the specimens are loaded to failure. And another specimens are loaded to failure after 24 hour cooling time. Tests were conducted at various temperatures ($20{\sim}700^{\circ}C$) for concretes made with W/B ratios 46%, 32% and 25%. Test results showed that the relative values of compressive strength and elastic modulus decreased with increasing compressive strength grade of specimen and the axial strain at peak stress were influenced by the load before heating. Thermal strain of concrete at high temperature was affected by the preload level as well as the compressive strength. Finally, model equation for compressive strength and elastic modulus of heated high strength concrete proposed by result of this study.

최근 고강도콘크리트의 압축강도, 탄성계수 및 최대하중에서의 변형에 대한 고온의 영향이 실험적으로 연구되어지고 있다. 본 연구는 40, 60, 80 MPa 급 고강도콘크리트의 재료 역학적 특성에 있어서 $20{\sim}700^{\circ}C$ 범위로 상승되는 온도의 영향을 연구하는데 그 목적이 있다. 본 연구에서는 설계하중 사전재하 및 잔존강도시험 방법으로서 시험체를 가열하기 전에 상온 압축강도의 25% 하중을 사전재하한 후 가열을 실시하고, 가열하는 동안 하중을 유지하며, 목표온도에 도달한 후 고온상태 및 상온에서 24시간 냉각상태에서 시험체가 파괴될 때까지 재하를 실시하였다. 시험은 W/B 46%, 32% 및 25%로 이루어진 콘크리트 시험체에 대하여 $20{\sim}700^{\circ}C$의 다양한 온도하에서 실시하였다. 시험 결과 콘크리트 강도가 증가할수록 고온에서의 상대적인 압축강도와 탄성계수는 감소하였으며, 최대하중에서의 축방향 변형은 설계하중 사전재하와 상관성이 높은 것으로 나타났다. 또한 온도상승에 따른 콘크리트의 열팽창 변형은 압축강도 뿐만 아니라 하중 크기의 영향을 받는 것으로 나타났으며, 최종적으로 가열을 받은 고강도콘크리트의 압축강도 및 탄성계수에 대한 모델식을 제안하였다.

Keywords

References

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Cited by

  1. Mechanical Properties of Concrete depending on Cooling Conditions After High Temperature Heating vol.12, pp.3, 2014, https://doi.org/10.3151/jact.12.82
  2. State-of-the-Art Research and Experimental Assessment on Fire-Resistance Properties of High Strength Concrete vol.18, pp.3, 2014, https://doi.org/10.11112/jksmi.2014.18.3.028