• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.813-816
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• 2006

Recently, improvements in the standard of living in industrial area require the establishment of a convenient residential environment in order to enhance the quality of living. To achieve such an environment, it is necessary to effectively reduce or prevent various environmental problems occurring in and around residential areas. Although conventional concrete has been regarded as a destroyer of nature, water and air can pass freely through concrete when it is made porous concrete by forming continuous void. In view of the harmony between nature and concrete, various research paths are being taken focusing on coarse aggregates to make porous concrete having continuous voids so as to improve water and air permeability, acoustic absorption, water purification, and applicability to vegetation. In this study, the Physical and Mechanical Properties of porous concrete according to compaction method analyzed by void ratio, coefficient of permeability and compressive strength.

• Computers and Concrete
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• 제15권2호
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• pp.141-166
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• 2015

In the present study, a Finite Element Model has been developed and used to study the effect of diameter to wall thickness ratio (D/t) of steel tube filled with concrete under axial loading on its behavior and load carrying capacity. The model is verified by comparing its findings with available experimental results. Influence of thickness and area of steel tube on strength, ductility, confinement and failure mode shapes has been studied. Strength enhancement factors, load factor, confinement contribution, percentage of steel and ductility index are defined and introduced for the assessment. A parametric study by varying length and thickness of tube has been carried out. Diameter of tube kept constant and equals to 140 mm while thickness has been varied between 1 mm and 6 mm. Equations were developed to find out the ultimate load and confined concrete strength of concrete. Variation of lateral confining pressure along the length of concrete cylinder was obtained and found that it varies along the length. The increase in length of tubes has a minimal effect on strength of tube but it affects the failure mode shapes. The findings indicate that optimum use of materials can be achieved by deciding the thickness of steel tube. A better ductility index can be obtained with the use of higher thickness of tube.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.775-780
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• 2002

Sandwich panel made by foamed styrene and ployuretane has been used generally in the construction area because of the high thermal conductivity and light weight but they occur harmful gases to both bodies and environments in the high temperature over $50^{\circ}C$. So, the purpose of this study is to investigate the physical properties of light-weight panel using the non-structural lightweight aggregate as a part of the substitution of foamed styrene and ployuretane. This paper dealt with the effect of the addition of polymer dispersion such as SBR, St/BA-1 and St/BA-2 having polymer-cement ratio as 5, 10, 15% and the filling ratio of continuous void as 50, 60% on the strength of polymer-modified sandwich panel core. From the results, we could know that the compressive and flexural strength of the sandwich panel core using non-structural lightweight aggregate and polymer dispersion such as SBR, St/BA-1 and St/BA-2 tended to be increased with an increase in the polymer-cement ratio and the filling ratio of continuous void.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.218-221
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• 2006

The past Korean Bridge Design Specifications have no limitation on the amount of lap splices of longitudinal bars in the plastic hinge zone of piers. A majority of bridge piers which have been non-seismically designed might have some lap splices in plastic hinge zone. Also a number of those piers in Korea have a low aspect ratio(height/section area). So, some problems such as low ductility behavior may happen. In this study, the real pier which was non-seismically designed and has a low aspect ratio was selected for the quasi-static tests. Two groups of full scaled RC pier models of which aspect ratios are about 2.26 and about 2.67 were fabricated. And then, quasi-static tests according to the drift level history method were implemented. From the test results, the failure of these test specimens have been shown in the complex shear-flexural or shear modes. The low aspect ratio and the lap splice have largely influenced on the seismic performance of bridge piers.

• 콘크리트학회논문집
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• 제12권3호
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• pp.21-30
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• 2000

Recently, reinforced concrete structures exposed to severe enviroment are increased in metropolitan area. The acid rain and CO2 penetrated towad rebar, thus rebar corrosion occurred. The corrosion of rebar in concrete is, as in most corrosion processes, an electrochemical nature. The corrosion may severely affect on durability and service life of such a concrete structures. This study was performed for the purpose of acquiring data about corrosion condition and considering a countermeasure to prevent rebar from corroding due to carbonation of concrete. An accelerated car bonation testing procedure was applied to measure the evolution of carbonation and rebar corrosion with time for various water-binder ratios and cement types.

• Computers and Concrete
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• 제10권1호
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• pp.35-47
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• 2012

The ideal gradating curve is used in this study to estimate densified aggregate blended ratio and total surface area of aggregate, there by under assigned paste amount of concrete, and coating paste thickness can then be deduced. Four groups of concrete mixtures were prepared and the corresponding concrete properties, such as workability, compression strength, ultrasonic velocity, surface resistivity and chloride ion penetration, were measured and finally the results are interpreted in terms of "coating thickness". The result shows as the coating thickness of the concrete is higher than critical one, the coating thickness on aggregate does affect the workability, and whatever workability is required the superplasticizer can be adjusted to achieve the demand workability. Under a fixed paste quality at the same age, coating paste thickness is inversely proportional to the concrete properties, especially as the coating thickness gets thinner.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.31-36
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• 2008

This study aims to examine the effects of thickness of the concrete members and curing temperature on the properties of low heat concrete through heat of hydration analysis. Type of the members that was analyzed in the experiment is ternary mixture of ordinary portland cement, blast-furnace slag incorporating ratio(20%) and fly ash incorporating ratio(30%), which formed a mat foundation. Thicknesses of the concrete members were 1, 2 and 3(m) and three levels of curing temperatures were 10, 20 and 30(℃). They were applied to analyze the effects on the temperature and thermal cracking index. As a result, for temperature history, temperature difference between the central area and the surface tended to decrease as the thickness of the concrete members get thinner. For the temperature cracking index, on the other hand, the risk of cracking tended to decrease as the curing temperature gets higher and as the thickness gets thinner.

• 콘크리트학회논문집
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• 제21권5호
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• pp.629-638
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• 2009

합성단면을 구성하는 콘크리트 단면에 크리프에 의한 장기변형이 발생되면 합성단면에는 추가의 변형이 발생되며 콘크리트 단면에는 장기변형의 일부구속으로 잔류응력이 발생한다. 이 논문에서는 복잡한 합성단면에서 콘크리트 단면의 장기변형에 대한 반응을 평가하는 기존의 단계별계산법을 보다 효율적으로 적용할 수 있도록 일반화 하였다. 장기변형이 발생하는 콘크리트 단면과 이 변형의 일부를 구속하는 구속단면의 단면특성과 재료특성으로부터 초기 합성단면의 환산단면특성이 유도되고, 각 단계의 크리프계수가 고려된 유효탄성계수가 적용된 환산 단면특성이 유도되었다. 합성단면의 일반화 반응에 대한 5개의 일반화 매개변수로 구성된 단계별계산법의 식이 유도되었다. 각 단계별 계산식에는 크리프계수의 증가가 일정하도록 하여 식의 단순화와 계산시간의 감축 및 균등한 단계별 계산오차가 가능한 균등 크리프 단계별계산법을 제안하였다. 콘크리트 단면의 초기 축방향 탄성 변형률에 대한 일반화 반응은 콘크리트 단면적의 비율에 가장 민감하고, 콘크리트 단면의 단면이차모멘트 비율보다는 구속단면의 단면이차모멘트 비율에 보다 민감하였다. 반면에 콘크리트 단면의 초기 탄성곡률에 대해서는 콘크리트 단면의 단면이차모멘트 비율에 가장 민감하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.465-468
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• 2008

본 연구는 영, 호남 지역의 레미콘 공장에서 현재 사용하고 있는 잔골재의 특성을 분석하고, 혼합사용 시 잔골재율 조정에 따른 콘크리트의 특성실험을 통하여 혼합사용 시 최적조건을 분석한 것으로 그 결과를 요약하면 다음과 같다. 영, 호남에서 사용하는 골재 종류별 물성은 조립률 및 0.08mm체 통과량을 제외하고 모두 KS F 2526 및 KS F 2527의 규정에 적합한 것으로 나타났는데, 각 공장에서는 단독사용이 부적합한 골재를 2종 이상 적절한 비율로 혼합사용하고, KS규정에 적합하게 품질을 관리하고 있었다. 영, 호남 각 공장에서 단위용적질량법에 의해 산출한 잔골재율로 조정한 콘크리트의 배합은 기존의 출하배합보다 높은 유동성을 보이는 것으로 나타났는데, 이는 잔골재율 약 2% 저감에 따라 잔골재의 표면적 감소 및 공극감소에 따른 시멘트 페이스트의 유동성에 미치는 잉여수량의 상대적 증가에 기인한 것으로 분석된다. 따라서 최적 잔골재율을 적용함으로써 단위수량 감소로 인한 경제적인 콘크리트 배합과 콘크리트의 내구성을 증진시키는 효과가 있을 것이라 사료된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.527-532
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• 1997

Design strength of structural members could be determined by applying a strength reduction factor to nominal strength. At the beginning point of the transition region for the strength reduction factor, P=0.1$\sigma$$_{ck}A_g$, only sectional area and concrete strength are adopted as the variables of P=0.1$\sigma$$_{ck}A_g$. Therefore, P=0.1$\sigma$$_{ck}A_g$ is the empirically adopted which does not consider steel ratio, steel yielding stress, and steel arrangement. So, this research was perpormed the computer program for the analysis of axial force-moment-curvature relationship of reinforced concrete columns by sectional behaviour nonlinear analysis using a concrete compressive stress-strain curve, in order to investigate the ductility of reinforced concrete columns. As a result, ductility indicies of axial force, P=0.1$\sigma$$_{ck}A_g$, represented the lack of consistency of the indicies value for the various sections.