• 레미콘
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• 7호통권72호
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• pp.29-41
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• 2002

The purpose of this study is to investigarte the mix design method and the mechanical properties of High stength Lightweight Concrete (HSLC). In the experment, concrete mixing was conducted to select the optimum mix design for HSLC in laboratory. Also, concrete mixing in ready mix design. As a result, it is possible to establish the mix design of HSLC according to the using these experimental results ;the estimate equation for unit weight of HSLC. the relationship between W/C and compressive strength of HSLC and the fluidity of HSLC in the view of workability

• Steel and Composite Structures
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• 제19권4호
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• pp.843-860
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• 2015

Recycled tire rubber-filled concrete (RRFC) is employed into the steel-concrete composite structures due to its good ductility and crack resistance. Push-out tests were conducted to investigate the static behavior of steel and rubber-filled concrete composite beam with different rubber mixed concrete and studs. The results of the experimental investigations show that large studs lead a higher ultimate strength but worse ductility in normal concrete. Rubber particles in RRFC were shown to have little effect on shear strength when the compressive strength was equal to that of normal concrete, but can have a better ductility for studs in rubber-filled concrete. This improvement is more obvious for the composite beam with large stud to make good use of the high strength. Besides that the uplift of concrete slabs can be increased and the quantity and width of cracks can be reduced by RRFC efficiently. Based on the test result, a modified empirical equation of ultimate slip was proposed to take not only the compressive strength, but also the ductility of the concrete into consideration.

• 콘크리트학회논문집
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• 제18권3호
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• pp.361-370
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• 2006

본 연구에서는 국내외 강섬유보강 콘크리트보의 실험값 및 이론식을 분석하여 강섬유의 보강효과 및 부재의 역학적 거동을 규명하였고, 기존의 휨강도식보다 더 정확하고 합리적인 휨강도식을 제안하였다. 제안된 휨강도식은 실험값과 좋은 일치를 보여주었고, 강섬유보강 콘크리트보의 휨강도식은 강섬유보강효과뿐만 아니라 철근의 변형률 경화효과도 함께 고려하는 것이 적절함을 알 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.43-48
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• 2001

The use of fly ash in cement and concrete industries has many benefits including engineering, economic, and ecological aspects. However, it has a disadvantage of low strength development, especially at early ages. In this study, in order to overcome this problem, the early strength accelerating agent($NA_{2}$ $SO_{4}$) was selected and applied to the production of high strength concrete(HSC) containing fly ash. It was found that the compressive strength of fly ash concrete incorporating TEX>$NA_{2}$ $SO_{4}$ has greater than that of concrete containing fly ash only until 7 days after casting. From the microstructural point of view, ettringite increased and pores decreased in fly ash concrete incorporating TEX>$NA_{2}$ $SO_{4}$ , leading to the development of early age strength. It was also found that the velocity vs. strength relationship of HSC is considerably different from that of low-strength concrete(LSC). Therefore, in order to predict early age strength of HSC, a estimation equation different from that for LSC is needed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.293-298
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• 1995

The strength of shear connectors embedded in lightweight concrete slab with deck plate is influenced by various factors of deck plate, shear conncetor and concrete. Generally, it is reported that the strength of shear connector in lightweight concrete decreases in comparison with that in normal concrete. So this paper is to use compressive strength of lilghtweight concrete, width-height ratio of deck plate, and cross sectional area of shear conncetor as variables, to evaluate the strength of shear conncetors in composite beam of steel and lilghtweight concrete slabs with deck plate, and then to suggest the reasonable strength equation by comparing the push-out test results with establixhed strength formula. As the result of 24 specimens test, in case of lightweight concrete slab with deck plate, it has showed that in the same strength, the strength of shear connector decreased about 10~20% in comparison with that in normal concrete. In spite of lightweight concrete, the test results were closely approached the established strength formula of shear connector using Fisher's reduction coefficient.

• Computers and Concrete
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• 제21권3호
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• pp.249-259
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• 2018

The use of recycled aggregate in concrete is gaining much attention due to the growing need for sustainability in construction. In the present study, Self Compacting Concrete (SCC) is made using both natural and recycled aggregate (crushed recycled concrete aggregate from building demolished waste) and performance of recycled aggregate based SCC for the bond behaviour of reinforcement is evaluated. The major factors that influence the bond like concrete compressive strength (Mix-A, B and C), diameter of bar ($D_b=10$, 12 and 16 mm) and embedment length of bar ($L_d=2.5Db$, $5D_b$ and full depth of specimen) are the parameters considered in the present study in addition to type of aggregates (natural and recycled aggregates). The mix proportions of Natural Aggregate SCC (NASCC) are arrived based on the specifications of IS 10262. The mix proportions also satisfy the guidelines of EFNARC. In case of Recycled Aggregate SCC (RASCC), both the natural coarse and fine aggregates are replaced 100% by volume with that of recycled aggregates. These mixes are also evaluated for fresh properties as per EFNARC. The hardened properties like compressive strength, split tensile strength and flexural strength are also determined. The pull-out test is conducted as per the specifications of IS 2770 (Part-1) for determining the bond strength of reinforcement. Bond stress versus slip curves were plotted and a typical comparison of RASCC is made with NASCC. The fracture energy i.e., area under the bond stress slip curve is determined. With the use of recycled aggregates, reduction in maximum bond stress is noticed whereas, the normalised maximum bond stress is higher in case of recycled aggregates. Based on the experimental results, regression analysis is conducted and an equation is proposed to predict the maximum bond stress of RASCC. The equation is in good agreement with the experimental results. The available models in the literature are made use to predict the maximum bond stress and compare the present results.

• 콘크리트학회지
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• 제9권1호
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• pp.105-113
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• 1997

콘크리트 실린더 공시체의 크기에 따른 압축강도의 감소현상은 많은 관심을 받아 왔으나, 지금까지도 이에 대해 제시된 모델식이 없는 실정이다. 기존의 연구결과에 의하면 콘크리트의 강도는 부재의 크기가 증가할수록 감소하며 그 파괴거동을 규명하기 위해서는 비선형 파기역학 이론을 적용해야 함을 알 수 있다. 이전의 연구에서 표준형 콘크리트 실린더 공시체의 크기에 따른 압축강도의 변화를 파괴역학 이론에 따라 연구하고 실용적인 예측 모델식을 제시한 바 있다. 이 논문에서는 높이/직경의 비가 2/1이 아닌 비표준형 실린더 공시체를 고려하여 보다 일반적인 실린더 압축강도 에측 모델식을 제시하고자 한다. 이를 위하여 최대골재크기가 미소균열영역에 미치는 영향을 이론적으로 고찰하였으며, 특성길이의 개념을 새로이 도입하여 일반화된 크기효과에 대한 모델식을 제시하였다. 이 연구의 결과는 기존 구조물에서 채취한 다양한 크기의 콘크리트 코아 강도 등을 예측하는데도 매우 실용적으로 사용될 수 있을 것이다.

• 한국식품과학회지
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• 제25권6호
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• pp.632-636
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• 1993

본 연구에서는 생선단백질의 젤형성에 영향을 미치는 처리조건(가열온도, 가열시간, 염농도)을 달리하여 형성되는 젤의 압축응력과 초음파의 잔존시간을 비교 분석하였다. 그 결과 가열온도가 증가할수록, 가열시간이 증가할수록 또한 염농도가 감소할수록 조직의 압축응력으로 나타내어지는 젤강도는 증가하였으나 그에 상응하는 초음파의 잔존시간은 감소하였으며 젤강도와 잔존시간이 반비례함을 보였다. 각 처리조건을 변수로 하여 중회귀분석을 한 결과 초음파의 잔존시간에 의해 계산 예측된 압축응력과 실측정값과 비교시 유사함을 나타내었다. 이와 같이 볼 때 초음파를 이용한 잔존시간의 측정은 식품조직내의 변화에도 민감한 변화를 나타내었으며 식품공정과정 중에 비파괴적인 방법으로의 사용여부도 기대되어진다.

• Structural Engineering and Mechanics
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• 제38권4호
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• pp.459-477
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• 2011

Due to the low elastic modulus of FRP, concrete members reinforced with FRP rebars show greater deflections than members reinforced with steel rebars. Deflection is one of the important factors to consider the serviceability of horizontal members. In this study flexural test of AFRP reinforced concrete beams was performed considering reinforcement ratio and compressive strength as parameters. The test results indicated that flexural capacity and stiffness increase in proportion to the reinforcement ratio. The test results were compared with existing proposed equations for the effective moment of inertia including ACI 440. The most of the proposed equations were found to over-estimate the effective moment of inertia while the equation proposed by Bischoff and Scanlon (2007) most accurately predicted the values obtained through actual testing.

• 콘크리트학회논문집
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• 제23권2호
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• pp.211-217
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• 2011

현행 설계기준식에 따르면 초고강도 콘크리트에서는 철근 인장 이음 길이보다 압축 이음 길이가 더 길어지는 현상이 발생된다. 압축 이음은 단부 지압이 존재하므로, 인장 이음보다 길 필요는 없다. 초고강도 콘크리트의 경제적 실용화를 위해 합리적인 압축 이음 강도의 평가가 필요하다. 이를 위해 설계강도 80, 100 MPa 콘크리트를 이용하여 횡보강근이 있는 압축 이음 실험을 수행하였다. 실험 결과 횡보강근량이 많을수록 압축 이음 강도는 향상되었다. 이음강도를 부착과 지압의 기여분으로 나눠서 분석하면, 이음 길이에 횡보강근량이 증가하여도 지압은 상승하지 않았다. 따라서 횡보강근 배근에 따른 압축 이음 강도의 상승은 부착 강도의 증가에 기인한 것으로 평가되었다. 실험 결과에서 분석된 이음 길이와 콘크리트 강도의 영향 특성을 고려하고, 기존 실험 자료를 통합하여 압축 이음 강도 평가식과 압축이음 길이 설계식을 제안하였다. 제안된 설계식을 이용하면 고강도 콘크리트 특성과 횡보강근 효과가 반영된 합리적인 압축 이음 길이가 산정되어 인장 이음 길이보다 길어지는 이상 현상을 해소할 수 있다.