• 한국강구조학회 논문집
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• 제13권1호
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• pp.19-28
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• 2001

본 연구에서는 강구조 휨재의 강도와 연서이을 실험적인 방법으로 조사하였다. 휨재의 성능평가와 관련하여 총 9개의 시험체를 제작하고 실험을 실시하였다. 4개의 시험체는 구조용 강재 SM490을 이용하여 제작하였으며 5개의 시험체 제작에는 구조용 강재SM570이 이용하였다. 실험결과는 시험체의 강도와 연성에 초점을 두고 분석하였다. 실험결과는 모든 시험체가 현행 한계상태 설계기준의 공칭휨강도를 평균 1.22배 초과하는 충분한 휨강도를 보유하는 것으로 나타났다. 그러나 강재 SM570으로 제작된 콤팩트 단면의 시험체는 요구되는 연성을 나타내지 못하였다. 강재 SM570의 항복비가 0.9이었으며 이러한 항복비가 연성이 부족한 원인으로 추정되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.5-8
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• 2005

The purpose of this study is to investigate the mechanical characteristics of plain and steel fiber high strength concrete under uniaxial and biaxial loading condition. A number of plain and steel fiber high strength concrete cubes having 28 days compressive strength of 82.7Mpa (12,000psi) were made and tested. Four principal compression stress ratios, and four fiber concentrations were selected as major test variables. From test results, it is shown that confinement stress in minor stress direction has pronounced effect on the strength and deformational behavior. Both of the stiffness and ultimate strength of the plain and fiber high strength concrete increased. The maximum increase of ultimate strength occurred at biaxial stress ratio of 0.5 in the plain high strength concrete and the value were recorded 30 percent over than the strength under uniaxial condition. The failure modes of plain high strength concrete under uniaxial compression were shown as splitting type of failure but steel fiber concrete specimens under biaxial condition showed shear type failure.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.105-108
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• 2006

Recently, trouble of sand supplying is occurred according to exhaustion of natural sand resources. Therefore various measures are proposed for solution of trouble of sand supply and crushed sand among measures is used as one of most universal measures. But because crushed sand have poor particle shape and plenty of mikes micro particle, the quality of concrete using crushed sand deteriorated. Therefore, this study evaluated engineering property of concrete with replacement ratio of crushed sand and EEZ sand applied evaluation result to fundamental data for quality control of concrete using crushed sand and EEZ sand and The result of this study have shown that quality of concrete using crushed sand and EEZ sand and The compressive strengh of concrete up to 50, 70% EEZ sand replacement by crush sand, nearly equal to that of general sand.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.67-68
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• 2015

Recently, usage of ultra-high strengh concrete(UHSC) have been increased. Concrete has been recognized as a material which is resistant to high temperatures, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. Therefore, this study evaluated effect of the coarse Aggregate volume by high temperature mechanical properties of UHSC. Residual mechanical properties are evaluated under fine aggregate ratio 40,60% and 500℃ temperature on UHSC of W/B 15, 20%. As result, residual mechanical properties of UHSC are high by lower coarse aggregate volume.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.23-31
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• 2015

CFST columns are structurally superior because the concrete inside the steel tubes prevents local buckling at the tubes and the tubes confine the concrete. And, the thickness of steel tube in CFST column has been thinner with development of high-strengh steel. The thinner the steel tube of a square CFST column is, the more local buckling is likely to occur. For this reason, we developed welded built-up square steel tube with stiffeners which are placed at the center of the tube width acts as an anchor. In this study, we conduct experimental test for three specimens of the 4m long span welded built-up square CFT column with parameters of L/D and D/t. And, the test results were compared with the analysis results by M-${\phi}$-P Program.

• 한국전산구조공학회논문집
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• 제15권3호
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• pp.535-543
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• 2002

본 논문의 목적은 전단하중을 받는 얇은 원통구조물의 세장비에 따른 좌굴특성을 보다 깊이 있게 검토하는 것이다. 이를 위하여 J. Okada 등이 제안한 좌굴평가식을 사용하여 세장비에 따른 좌굴강도 평가를 수행하였다. 좌굴강도 평가 결과들로부터 세장비 L/R=3.1, 1.6, 그리고 1.0을 갖는 세가지 좌굴시험체를 결정하고 이에 대한 수치해석과 좌굴특성시험을 수행하였다. 그 결과, 세장비 L/R=3 이상인 경우 평가식에서 예측된 바와 같은 굽힘좌굴이 지배적으로 나타났으며 세장비 L/R=1.0이하로 작을 경우에는 전단좌굴이 지배적으로 나타났고, 세장비 L/R=1.6 영역에서는 전단과 굽힘좌굴이 동시에 발생하는 복합자굴 특성이 나타났다 그리고 수치해석과 평가식에 의한 좌굴특성평가 결과는 시험결과들과 잘 일치하였다.

• 콘크리트학회지
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• 제7권2호
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• pp.155-164
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• 1995

본 연구는 증기양생을 실시하는공장제품을 대상으로 석고계 고강도콘크리트용 혼화재를 사용하여 콘크리트를 고강도화하는데 그 목적이 있다. 목표 슬럼프는 원심력 성형제품을 대상으로 슬럼프 $6{\pm}1cm$가 되도록 고성능감수제로 조절하였으며, 아울러 양생방법에 다른 고강도콘크리트용 혼화재를 사용한 콘크리트의 강도발현 특성을 검토하고자 증기 및 수중양생을 실시 비교하였다. 실험결로부터 고강도 콘크리트용 혼화재는 증기양생이 효과적이며 압축강도 발현은 단위결합재량 $530{\sim}600kg/m^3$의 조건에서 10%치환으로 무치환에 비하여 1.3배 증가된 $650kgf/cm^2$ 이상, 15-30% 치환시 1.4-1.5배 증가된 $700kgf/cm^2$이상을 얻었다. 따라서 고강도콘크리트용 혼화재는 증기양생시의 고강도콘크리트 제조에 효과적으로, 시멘트2차제품 제조에 오오토클레브 양생을 하지 않고 증기양생만으로 고강도콘크리트를 얻을 수 있는 유효한 혼화재임을 나타냈다.

• 한국강구조학회 논문집
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• 제14권1호
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• pp.51-58
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• 2002

고층 건물의 층고를 줄이기 위해, 역 T형강, PC 콘크리트 그리고 현장타설 콘크리트 슬래브로 이루어진 새로운 합성보로써 TEC-BEAM이 개발되었다. TEC-BEAM은 이전에 단순보 실험이 수행되었고, 우수한 거동을 보였다. 그러나 현장적용을 위해서는 TEC-BEAM의 상주주근을 정착시키기 위해 철골 브라켓을 이용하는 모멘트저항 접합부 상세가 요구되었다. 본 연구에서는 TEC-BEAM 접합부에 대한 3개의 실험체를 실험하였고 실험변수는 (1)횡철근 간격. (2)브라켓 길이에 대한 철근의 배근폭비이다. 실험체는 Eurocode 4에 의한 Semi-Rigid Full Strengh 접합부로 분류되었다. 실험결과로부터 제안된 시스템은 우수한 성능을 보이며 현장에서 적용될 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1193-1196
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• 1993

Electrical properties of $C_{22}$-Quinolium(TCNQ) Langmuir-Blodgett(LB) films are reported depending on a type of applied voltage on a type of applied voltage and temperature. A conductivity was identified to be anisotropic with a ratio of ${\sigma}||/{\sigma}{\bot}{\simeq}10^7$ at room temperature. The I-V characteristics along the film surface direction show an ohmic behavior up to a few hundred volts. But the I-V characteristics in the vertical direction display an ohmic behavior for low-electric field, and a nonohmic behavior for high-electric field. This nonohmic behavior has already been interpreted as a conduction mechanism of space-charge limited current and Schottky effect near the electric-field strengh of $10^6$ V/cm. When the electric field exceeds further, there is anormalous phenomia similiar to breakdown. From the study of I-V characteristics with the application of step or pulse voltage, we have found that the breakdown voltage shifts to higher one as the step or pulse interval becomes shorter. These results indicate that the breakdown is due to both electrical and thermal effect. To see the infulence of temperature, current was measured as function of temperature with several bias voltages, which are lower than that of breakdown. It shows that the current increases about 3 orders of magnitude near $60{\sim}70^{circ}C$, and remains constant for a while up to $140^{\circ}C$ and then suddenly drops. Arahidic acid was used to cmpare with $C_{22}$-Quinolium(TCNQ) LB films.

• Journal of Preventive Medicine and Public Health
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• 제17권1호
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• pp.251-257
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• 1984

Low birth weight baby, defined as the baby born with less than or equal to 2,500g of body weight by WHO has been a great concern in the fold of maternal and child health since the low birth weight is a major cause of high perinatal mortality. Any measure to prevent the low birth weight baby is most desirable not only for saving the life of a baby but also for levelling up the health of the whole society. The authors attempted to figure out how some known maternal risk factors are related to the low birth weight and to measure their strengh of associations in terms of relative risk using hospital birth records. For this study, hospital birth records of 66 low birth weight cases and sex-parity matched 198 normal controls were chosen from Kangnam St. Mary's Hospital, Catholic Medical Center, and the data were analyzed in regards to several maternal factors. The risk factors studied were mother's age, mother's ABO blood type, previous histories of abortion, low birth weight baby, fetal wastage, and maternal diseases represented by anemia, hypertension, proteinuria, and glucosuria. The results obtained in this study were as follows: 1. The mean body weight of the cases and controls were 1,955g and 3,251g, respectively, and the heights were 41cm for cases and 50cm for controls. Mean gestation periods of cases and controls were 34 weeks and 39 weeks, respectively. 2. Young mother(less than or equal to 20 years of age) or old mother(more than or equal to 30 years of age) experienced more frequently the delivery of low birth weight babies than mothers in between 21 and 29 years of age. But the difference was not statistically significant. 3. Mothers whose blood type was O tended to have slighty higher frequency of low birth weight babies while B mothers have lower frequency. But the difference was not statistically significant too. 4. Those mothers who had experienced low birth weight baby in the past tended to give more births of low birth weight babies. This factor is even statistically significant and the relative risk of the prior experience of low birth weight was 6.7. 5. Mothers with experience of fetal losses and mothers of more than two pregnancies had higher frequency of low birth weight than the mothers with no fatal losses and of first pregnancy, but the difference was not statistically significant. 6. Statistically significant higher frequency of low birth weight were found in mothers with hypertension(odds ratio=4.07), anemia(odds ratio=22,33), and proteinuria(odds ratio=2.79). In summary, these study results strongly suggest that in order to prevent the low birth weight, special care should be made when the mother is too young or too old, and when the mother has experienced deliveries of low birth weight and fetal deaths. Medical control for the maternal diseases such as anemia and hypertension is also needed before or during the pregnency.