• Title, Summary, Keyword: 수축

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Shrinkage Stress Analysis of Concrete Slab with Shrinkage Strip in Multi-Story Building (수축대를 사용한 고층건물 콘크리트 슬래브의 건조수축응력 해석)

  • 김한수;조석희
    • Journal of the Korea Concrete Institute
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    • v.14 no.5
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    • pp.726-733
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    • 2002
  • Shrinkage strip or separation strip is a temporary joint that is left open for a certain time during construction to allow a significant part of the shrinkage to take place without inducing stress. A shrinkage stress analysis method of shrinkage strip in concrete slab of multi-story building considering the relaxation effect of creep and construction sequence is proposed. The analysis results of 10-story example building show that the effect of shrinkage strip can be analyzed easily by the proposed method. And shrinkage strip installed in a particular floor makes the stress of that floor reduced and the stress of the other floors increased a little. The rate and amount of stress reduced with closing time mainly depends on the development of shrinkage with time of concrete model used. The amount of stress reduced is determined by the amount of shrinkage strain developed before the closing of shrinkage strip.

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.

Shrinkage Properties of High Performance Concrete with Shrinkage Reducing Agent (수축저감제를 사용한 고성능 콘크리트의 수축특성)

  • Koh, Kyung-Taek;Kim, Do-Gyeum;Han, Cheon-Goo;Lee, Jang-Hwa
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.1
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    • pp.181-188
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    • 2005
  • Generally, high performance concrete has characteristics such as low water-cementitous material ratio, lots of unit binder powder, thus the drying shrinkage and autogenous shrinkage are tend to be increased. The purpose of this study is to investigate the effect of the glyclos based shrinkage reducing agent on the drying shrinkage and autogenous shrinkage of high performance concrete with 30% of water-cemetitious material ratio as a study to develop the technology to reduce the concrete shrinkage. Test results show that the drying and autogenous shrinkage of high performance concrete are reduced by about 20~35% at the mixing ratio of shrinkage reducing agent of 0.5%, and 1.0%, compared with plain concrete. Therefore, it analyze that the using of shrinkage reducing agent is effective to reduce the drying shrinkage and autogenous shrinkage of high performance concrete.

A Study on the Plastic Shrinkage Properties of Cement Mortars (시멘트 모르터의 소성수축 특성에 관한 연구)

  • 이의학;김범수;송영진;송명신;이경희;박한수
    • Journal of the Korean Ceramic Society
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    • v.38 no.8
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    • pp.716-723
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    • 2001
  • 시멘트 모르터의 소성수축에 의한 균열을 방지하기 위해 소성수축 특성에 관한 연구를 수행하였다. 우리나라 봄철의 대표적인 기후인 온도 20$\pm$3$^{\circ}C$, 상대습도 55%, 풍속 3.5m/s의 기후조건으로 하였으며, 모르터의 물 시멘트 비, 시멘트 골재 비, 팽창재 사용, 플라이 애쉬 치환, 수분증발을 억제하기 위한 중점제 등을 사용하여 소성수축의 특성을 검토하였다. 연구 결과 소성수축 변형은 응결시간과 밀접한 관계가 있으며 응결시간이 빠를수록 변형은 크게 나타났다. 또한 물시멘트 비에 의해서도 소성수축 변형은 큰 것으로 나타났다. 모르터에서의 골재 비율이 작거나, 플라이 애쉬의 치환율이 클수록 소성수축 변형은 매우 크게 나타났다. 중점제의 사용은 소성수축 변형을 줄이는데 효과가 있었으며, 건조수축 보상용 팽창재의 사용은 소성수축 변형율을 크게 하는데 이는 ettringite 생성에 의한 물 시멘트 비의 감소효과를 가져오기 때문이다.

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수축포장의 특성 및 수축필름

  • 한국포장협회
    • The monthly packaging world
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    • pp.101-108
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    • 1993
  • 수축포장은 완구, 식품, 잡화 등 불규칙한 형상의 상품을 타이트하게 포장하여 상품의 가치를 높게 하기 위해 주로 사용되고 있다. 또한 여러 개의 상품을 한번에 포장함으로써 포장비 절감과 운반중 진동이나 충격으로부터 상품을 보호하는 효과를 위해서도 흔히 쓰인다. 수축포장의 특성에 따라 수축필름도 달라지는데 여기서는 PE, PP, PET 수축필름에 대해 살펴본다.

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POLYMERIZATION SHRINKAGE KINETICS OF SILORANE-BASED COMPOSITES (Silorane 복합레진의 중합수축의 동력학)

  • Kwon, Young-Chul;Lee, In-Bog
    • Restorative Dentistry and Endodontics
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    • v.35 no.1
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    • pp.51-58
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    • 2010
  • Dental composites have improved significantly in physical properties over the past few decades. However, polymerization shrinkage and stress is still the major drawback of composites, limiting its use to selected cases. Much effort has been made to make low shrinking composites to overcome this issue and silorane-based composites have recently been introduced into the market. The aim of this study was to measure the volumetric polymerization shrinkage kinetics of a silorane-based composite and compare it with conventional methacrylate-based composites in order to evaluate its effectiveness in reducing polymerization shrinkage. Five commercial methacrylate-based (Beautifil, Z100, Z250, Z350 and Gradia X) and a silorane-based (P90) composites were investigated. The volumetric change of the composites during light polymerization was detected continuously as buoyancy change in distilled water by means of Archemedes' principle, using a newly made volume shrinkage measurement instrument. The null hypothesis was that there were no differences in polymerization shrinkage, peak polymerization shrinkage rate and peak shrinkage time between the silorane-based composite and methacrylate-based composites. The results were as follows: 1. The shrinkage of silorane-based (P90) composites was the lowest (1.48%), and that of Beautifil composite was the highest (2.80%). There were also significant differences between brands among the methacrylate-based composites. 2. Peak polymerization shrinkage rate was the lowest in P90 (0.13%/s) and the highest in Z100 (0.34%/s). 3. The time to reach peak shrinkage rate of the silorane-based composite (P90) was longer (6.7 s) than those of the methacrylate-based composites (2.4-3.1 s). 4. Peak shrinkage rate showed a strong positive correlation with the product of polymerization shrinkage and the inverse of peak shrinkage time (R = 0.95).

Shrinkage Properties of High Performance Concrete Used Expansive Additive and Shrinkage Reducing Agent (팽창재와 수축저감제를 사용한 고성능 콘크리트의 수축 특성)

  • Koh, Kyung Taek;Park, Jung Jun;Ryu, Gum Sung;Kang, Su Tae
    • Journal of The Korean Society of Civil Engineers
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    • v.26 no.4A
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    • pp.787-794
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    • 2006
  • Generally, high performance concrete has characteristics such as low water-cementitious material ratio, lots of unit binder powder, thus the heat of hydration, autogenous shrinkage are tend to be increased. This study is to investigated the effect of the expansive additive and shrinkage reducing agent on the shrinkage properties of high performance concrete as a study to develop the reduction technology of the concrete shrinkage. Test results showed that the expansive additive and shrinkage reducing agent were effective the reduction of shrinkage of high performance concrete. Especially, the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separately using method of that. Also, it analyzed that the combination of expansive additive of 5% and shrinkage reducing agent of 1% was the most suitable mixture, considering to the fluidity, strength and shrinkage properties.

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Multi-physics Modelling of Moisture Related Shrinkage in Concrete (콘크리트 수분관련 수축에 관한 다중물리모델)

  • Lee, Chang-Soo;Park, Jong-Hyok
    • Journal of Korean Society of Hazard Mitigation
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    • v.9 no.2
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    • pp.1-9
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    • 2009
  • Water binder ratio combine high-performance concrete shrinkage of less than 0.4 to determine the transformation to a total shrinkage of water to move outside and internal consumption of moisture due to drying shrinkage and autogenous shrinkage, and then, the relative humidity changes and strain to be approached by surface physics describe the relationship between self-desiccation and autogenous shrinkage was set. To verify the self-desiccation in the humidity shrinkage and humidity measurements performed, and the research model, Tazawa, CEB-FIP model than to let the measure and the most similar results in this study based on self-desiccation model, autogenous shrinkage didn't represent the linear shrinkage by the drying shrinkage of the external moving but exponential relationships, unlike with the nature and rapid in the early age properly describes the attributes in shrinkage could see. After this research to move moisture and to reflect the shrinkage model, temperature, moisture transfer, strain analysis by multi-physics model is very similar to the results of mock-up specimen measurements performed for this research, the value measured by the internal consumption of moisture, therefore self-desiccation and a multi-physics model considering autogenous shrinkage might be relevant.

Effects of Specimen Shape on Hydration Heat and Autogenous shrinkage at an early (시험체 형상에 따른 고강도 콘크리트의 수화열 및 자기수축 초기특성 분석)

  • Lee, Eui-Bae;Koo, Kyung-Mo;Kim, Young-Sun;Kim, Young-Duck;Kim, Gyu-Yong;Kim, Moo-Han
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.915-918
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    • 2008
  • Hydration heat and autogenous shrinkage are generated essentially by the same hydration. Many researchers have studied the close relationship between hydration temperature and autogenous shrinkage but hardly any research has been undertaken to explain the specific numerical relation. In this study, early age properties of hydration heat and autogenous shrinkage of specimen whose section size was changed were analyzed, and relationship between hydration heat and autogenous shrinkage was investigated. In the results of the study, inner temperature and autogenous shrinkage increased as the section size increased. And rise and rise ratio of hydration temperature and autogenous shrinkage in hydration heating section and autogenous shrinking section are increased too. Temperature rise and autogenous shrinkage rise increased respectively, as hydration heating velocity and autogenous shrinking velocity increased. And autogenous shrinkage rise and autogenous shrinking velocity increased as hydration heating velocity increased.

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Observation of Shrinkage Features of Cross Sectional Surface of Wood by LV-SEM (저진공주사현미경(LV-SEM)을 이용한 목재횡단면의 수축거동관찰)

  • Kang, Chunwon;Matsumura, Junji;Kang, Wook
    • Journal of the Korean Wood Science and Technology
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    • v.36 no.3
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    • pp.17-23
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    • 2008
  • The purpose of this study is to estimate the shrinkage of wood by LV-SEM (Low-Vacuum Scanning Electron Microscope) which can observe wetted wood sample. The shrinkage of small sample specimen by the dehumidification in the specimen chamber was investigated and compared with that of normal wood specimen. The observation of cross sectional surface of wood from wetted condition to dried condition can be achieved in about twenty minutes by means of the dehumidification in the specimen chamber of LV-SEM. The volumetric shrinkage of earlywood was almost the same as that of latewood. The shrinkage of SEM observation specimen was similar to that of normal wood specimen. From the correlation of the shrinkages between SEM observation specimen and normal wood specimen, it is surmised that the shrinkage of wood is more strictly dominated by shrinkage of latewood than that of earlywood.