• Title, Summary, Keyword: 부등수분분포

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Prediction of Differential Drying Shrinkage in Concrete (콘크리트의 부등건조수축에 관한 연구)

  • 김진근;이칠성
    • Magazine of the Korea Concrete Institute
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    • v.9 no.2
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    • pp.153-161
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    • 1997
  • In the concrete st~uctures exposed to the environmental condition, the water movement is occurred by thc moisture difilsion, and the rnoisturrt distribution in concwt.c is nonunifhrm. Such a non-unif'orm moisture distribution causes tht. diflbrent.ia1 drying shrinkage in concrete structures. From this typc. of' dif'fercntial drying shrinkagr' tensiit-1 stress is occurred in exposure surface of concrete structures. and may result in crack formation. This residual stress is significantly affected by the creep of concrete, and the differential creep is also occurred at the cross section of concrete structures due to moisture difference at each locations. In this study, based on the moisture diffusion theory, a finite element program which is capable of simulating the moisture distribution in concrete was developed. And the analysis method for the differential drying shrinkage was suggested, in which the differential creep was considered. The differential drying shrinkage strain was also measured at various positions of concrete. Finally the validity of analysis method was proved by comparing test results with analytical results.

Differential Drying Shrinkage of concrete an Early Ages Considering Self-desiccation (자체건조를 고려한 초기재령 콘크리트의 부등건조수축)

  • 김진근;이칠성
    • Magazine of the Korea Concrete Institute
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    • v.10 no.5
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    • pp.197-204
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    • 1998
  • 초기재령에서 외기에 노출된 콘크리트는 수분확산으로 인하여 부등건조수축이 발생하고, 또한 자체건조로 인하여 자기수축도 발생한다. 따라서 콘크리트 재부의 수축변형도는 이러한 자기수축을 포함하고 있으므로 이를 고려해야 한다. 본 연구에서는 초기재령에서 콘크리트 강도에 따라 자기수축의 영향을 고려하여 부둥건조수축에 대한 실험과 해석을 수행하였다. 또한 콘크리트 내부의 부등수분분포로 인한 수축변형도에 대하여 실험결과와 해석결과를 비교하여, 해석방법의 타당성을 검증하였다. 실험 및 분석결과에 의하면 저강도콘크리트는 수분확산으로 인하여 주로 수축현상이 일어나고 자기수축의 영향은 거의없었다. 그렇지만 고강도 콘크리트는 자기수축에 의해서도 영향을 받았다. 그리고 콘크리트의 부등건조수축은 강도에 따라 큰 차이를 나타냈다. 또한 제시한 해석방법에 의한 해석결과는 실험결과를 잘 예측하였다.

Column Shortening of SRC Columns Considering the Differential Moisture Distribution (부등수분분포를 고려한 SRC 기둥의 축소량에 관한 연구)

  • Seol, Hyun-Cheol;Kim, Yun-Yong;Kwon, Seung-Hee;Kim, Han-Soo;Kim, Jin-Keun
    • Journal of the Korea Concrete Institute
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    • v.18 no.1
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    • pp.29-36
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    • 2006
  • Steel reinforced concrete(SRC) columns, which have been widely employed in high-rise buildings, exhibit a time-dependent behavior because of creep and shrinkage of concrete. This long-term behavior may cause a serious serviceability problem in structural systems, so it is very important to predict the deformation due to creep and shrinkage of concrete. However, it was found from the previous experimental studies that the long-term deformation of SRC columns was quite dissimilar from that of RC columns. A new method is required to quantitatively predict the long-term deformation of SRC columns. In this study, the causes of the discrepancy between the behaviors of RC and SRC columns are investigated and discussed. SRC columns exhibit a time-dependent relative humidity distribution in a cross section differently from that of reinforced concrete(RC) columns owing to the presence of a inner steel plate, which interferes with the moisture diffusion of concrete. This relative humidity distribution may reduce the drying shrinkage and the drying creep in comparison with RC columns. Therefore it is suggested that the differential moisture distribution should be taken into account in order to reasonably predict column shortening of SRC columns.

Development of Environmental Load Calculation Method for Airport Concrete Pavement Design (공항 콘크리트 포장 설계를 위한 환경하중 산정방법 개발)

  • Park, Joo-Young;Hong, Dong-Seong;Kim, Yeon-Tae;Jeong, Jin-Hoon
    • Journal of The Korean Society of Civil Engineers
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    • v.33 no.2
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    • pp.729-737
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    • 2013
  • The environmental load of concrete pavement can be categorized by temperature and moisture loads, which mean temperature distribution, and drying shrinkage and creep in the concrete slab. In this study, a method calculating the environmental load essential to mechanistic design of airport concrete pavement was developed. First, target area and design slab thickness were determined. And, the concrete temperature distribution with slab depth was predicted by a pavement temperature prediction program to calculate equivalent linear temperature difference. The concrete drying shrinkage was predicted by improving an existing model to calculate differential shrinkage equivalent linear temperature difference considering regional relative humidity. In addition, the stress relaxation was considered in the drying shrinkage. Eventually, the equivalent linear temperature difference due to temperature and the differential shrinkage equivalent linear temperature difference due to moisture were combined into the total equivalent linear temperature difference as terminal environmental load. The environmental load of eight civilian and two military airports which represent domestic regional weather conditions were calculated and compared by the method developed in this study to show its application.

Prediction of Time-dependent Moisture Diffusion Coefficient in Early-age Concrete (초기재령 콘크리트의 시간 의존적인 수분확산계수 예측에 관한 연구)

  • Kang, Su-Tae;Kim, Jin-Keun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.4
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    • pp.141-148
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    • 2005
  • The nonlinear humidity distribution occurs due to the moisture diffusion when a concrete is exposed to an ambient air. This nonlinear humidity distribution induces shrinkage cracks on surfaces of the concrete. Because shrinkage cracks largely affect the durability and serviceability of concrete structures, the moisture diffusion in concrete must be investigated. The purpose of this paper is to propose a model of the moisture diffusion coefficient that governs moisture diffusion within concrete structures. To propose the model, numerical analysis was performed with several experiments. Because the moisture diffusion coefficient is changed with aging, especially at early ages, the proposed model includes aging effect by terms of the porosity as well as the humidity of concrete.

Multi-physics Model of Moisture Related Shrinkage on Lightweight and Normal Concrete (경량콘크리트 및 일반콘크리트의 수분관련 수축에 대한 다중물리모델)

  • Lee, Chang-Soo
    • Journal of the Korea Concrete Institute
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    • v.22 no.2
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    • pp.159-169
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    • 2010
  • A multiphysics model analysis including moisture transport, heat transfer and solid mechanics and experiments on the normal and light weight concrete were carried out in order to study the effect of preabsorbed water in the light weight aggregates on the drying and shrinkage characteristics of concrete. Consequently, with fixed water-cement ratio, loss of water content of normal and light weight concrete were compared and the results showed that the lightweight concrete lost less moist than the normal concrete in early age and long term which was by moist supply effect. Accordingly, shrinkage strain size and distribution of lightweight concrete were decreased, and shrinkage reducing effect was efficient in early age with water cement ratio 0.3 and in both early age, and long term with water cement ratio 0.5. The comparison of analysis results and exaperimental results indicate that characteristic values of moisture transport and the relation humidity and shrinkage strain from this study are resonable for application for other differential shrinkage analysis in lightweight concrete.