• Title, Summary, Keyword: differential moisture distribution

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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.

Influence of Differential Moisture Distribution on SRC Column Shortening

  • Seol Hyun-Cheol;Kim Jin-Keuna;Kim Yun-Yonga;Kwon Seung-Heea
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.423-426
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    • 2005
  • Steel reinforced concrete (SRC) columns, which are widely employed in high-rise buildings, exhibit particular time-dependent behavior due to creep and shrinkage of the concrete, and this behavior may cause problems related to serviceability and structural stability. SRC columns also exhibit a time-dependent, cross-sectional relative humidity distribution that differs from reinforced concrete (RC) columns, due to the presence of an inner steel plate, which interferes with the moisture diffusion of concrete. This differential moisture distribution of SRC columns may reduce the drying shrinkage and the drying creep as contrasted with RC columns. Therefore, we propose that the differential moisture distribution be taken into account to accurately predict SRC column shortening.

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An Experimental Study on The Differential Dry Shrinkage of Concrete Using Artificial Lightweight Aggregate (인공 경량골재를 사용한 콘크리트의 부등 건조수축에 관한 실험적 연구)

  • Lee, Chang-soo;Kim, Young-ook;Lin, Yan
    • Journal of the Society of Disaster Information
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    • v.6 no.1
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    • pp.78-90
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    • 2010
  • Exposure to the outside, the concrete is differential moisture distribution depending on the depth. Such a differential moisture distribution causes the differential drying shrinkage in concrete structures. This thesis is researched to compare the shrinkage of lightweight concrete depending on depth to normal concrete. It is used artificial lightweight aggregate which has 20% of pre-absorb value by lightweight concrete. When water-binder ratio is 30%, average shrinkage of lightweight concrete section decreased than normal concrete, but differential shrinkage of lightweight concrete section increased. However water-binder ratio is 40% and 50% average shrinkage and differential shrinkage of lightweight concrete section decreased than normal concrete.

Study on moisture transport in concrete in atmospheric environment

  • Zhang, Weiping;Tong, Fei;Gu, Xianglin;Xi, Yunping
    • Computers and Concrete
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    • v.16 no.5
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    • pp.775-793
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    • 2015
  • Moisture transport in concrete in atmospheric environment was studied in this paper. Based on the simplified formula of the thickness of the adsorbed layer, the pore-size distribution function of cement paste was calculated utilizing the water adsorption isotherms. Taking into consideration of the hysteresis effect in cement paste, the moisture diffusivity of cement paste was obtained by the integration of the pore-size distribution. Concrete is regarded as a two-phase composite with cement paste and aggregate, neglecting the moisture diffusivity of aggregate, then moisture diffusivity of concrete was evaluated using the composite theory. Finally, numerical simulation of humidity response during both wetting and drying process was carried out by the finite difference method of partial differential equation for moisture transport, and the numerical results well capture the trend of the measured data.

The Prediction of Moisture Distribution in Concrete (콘크리트 내부의 수분분포 예측에 관한 연구)

  • 김진근;이칠성
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.123-128
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    • 1996
  • Water in concrete has an effect on properties of concrete very much, such as shrinkage, creep, fire resistance, durability, freezing and thawing resistance. Therefore predicting the moisture distribution in concrete is very important. And since the diffusion process of water in concrete is strongly dependent on the temperature and pore humidity, the process is highly nonlinear phenomena. In this study, a finite element program which was capable of simulating the moisture distribution in concrete was developed, and differential drying shrinkage due to the water diffusion process was measured at the different positions of concrete. This F.E.M. program is shown that the analytical results of this study are in good agreement with experimental data. Shrinkage strain caused by moisture distribution was increased with the decrease of pore relative humidity.

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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.

Study on the Long-term Behavior of SRC Columns Considering the Differential Moisture Distribution in a Section (단면 내의 부등수분분포를 고려한 SRC 기둥의 장기거동에 관한 연구)

  • Seol Hyun-Cheol;Kim Jin-Keun;Kim Yun-Yong;Kwon Seung-Hee;Kim Han-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.109-112
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    • 2004
  • It was found from the previous experimental studies that the long-term deformation of SRC columns was quite different from that of RC columns. A new approach method is needed to quantitatively predict the long-term deformation of SRC columns. In this study, the causes of the difference 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 RC columns due to the presence of a flange, which interferes with the moisture diffusion of concrete. This different relative humidity distribution may reduce the drying shrinkage and the drying creep in comparison with RC columns.

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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.

Phytosociological Distribution and Type of Glehnia littoralis Fr. Schmidt ex Miq. Community in Eastern Coast of Korea - Analysis by DCA ordination - (동해안 갯방풍군락의 형태와 식물사회학적 분포 - DCA배열법 분석 -)

  • Kim, Seong-Min;Song, Hong-Seon
    • Korean Journal of Medicinal Crop Science
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    • v.17 no.2
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    • pp.139-144
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    • 2009
  • This study was conducted to evaluate the vegetation, distribution and growth pattern of Glehnia littoralis community by the DCA ordination method in eastern coast of Korea. The number of plant species growth with G. littoralis in natural habitat was found 51 taxa, and species of high frequency among 51 taxa was Ixeris repens, Calystegia soldanella, Carex kobomugi, Elymus mollis, Lathyrus japonica and Zoysia macrostachya. Indicator species of Z. macrostachya, Linaria japonica, C. soldanella, I. repens, Carex pumila, Artemisia capillaris, Oenothera biennis, L. japonica and E. mollis in G. littoralis community was differential species of syntaxonomy. C. kobomugi, Z. macrostachya, E. mollis, Cynodon dactylon and L. japonica was the distribution in dryness sand and moisture sandyloam, I. repens, C. soldanella, L. japonica and C. pumila was the distribution in dryness sand. In coastal dune, I. repens, C. soldanella, Salsola komarovi and G. littoralis combined strength of the distribution, and sand of coast was typical of the habitat.

Stress Analysis for Differential Drying Shrinkage of Concrete (콘크리트의 부등건조수축으로 인한 응력의 해석)

  • 김진근;김효범
    • Magazine of the Korea Concrete Institute
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    • v.6 no.4
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    • pp.102-112
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    • 1994
  • The drying shrinkage of concrete has a close relation to the water movement. Since the diffusion process of water in concrete is strongly dependent on the temperature and the pore humidity, the process is highly nonlinear phenomena. This study consists of two parts. The first is the development of a finite element program which is capable of simulating the rnoisture distri- ,bution in concrete, and the other is the estimation of the differential drying shrinkage and stress considering creep by using the modified elastic modulus due to inner temperature change and maturity. It is shown that the analytical results of this study are in good agreement with experlimental data in the literatures, and results calculated by BP-KX model. The internal stress caused by moisture distribution which was resulted from the diffusion process, was calculated :quantitatively. The tensile stress which occured in the drying outer zone mostly exceeded the tensile strength of concrete, and necessarily would result in crack formation.