• 한국농공학회논문집
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• 제48권4호
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• pp.23-30
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• 2006

This study is performed to evaluate flowability of high flowable concrete using ordinary portland cement, crushed coarse aggregate, crushed sand, sea sand, fly ash, lime powder and superplasticizer. The slump flow and air content are increased with increasing the content of lime powder. But, the O-type funneling time and Box-type passing are decreased with increasing the content of lime powder. The slump flow, air content, O-type funneling time, Box-type passing and L-type filling of target compressive strength 21-27 MPa and 35-42 MPa at curing age 28 days are 47-50 cm and 56-60 cm, 4.2-5.5% and 4.0-5.7%, 8-12s and 5-10s, 4.3-5.0 cm and 3.4-5.0 cm, and excellent, respectively. These concrete can be used for high flowable concrete.

• 한국농공학회논문집
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• 제46권4호
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• pp.57-63
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• 2004

This study was performed to evaluate flow properties of polypropylene fiber reinforced high flow concrete. Test results were showed that the slump, slump flow and L-type compacting were decreased with increasing the content of polypropylene fiber. But, the Box-type passing and air content were increased with increasing the content of polypropylene fiber. The slump was $25.5{\sim}27.5cm$, the slump flow was $60{\sim}65cm$, the Box-type passing was $2{\sim}6cm$, the L-type compacting was excellent and air content was $2.7{\sim}3.2cm%$ by the polypropylene fiber content 0.2%, respectively. This concrete can be used for high flow concrete.

• 한국농공학회논문집
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• 제46권7호
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• pp.55-67
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• 2004

In this paper, the flowability, strengths, impact resistance and sulfuric acid resistance of steel fiber reinforced high performance concrete (SFHPC) for the steel fiber content and fly ash and blast furnace slag as admixtures were presented. For evaluating flowability particularly, tests of slump flow, box-type passing ability and L-type filling ability were performed. The slump flow of SFHPC was some decreased with increase of the steel fiber content. At the box-type passing ability, the difference of box height of SFHPC is greatly increased with increasing the fiber content. The L-type filling ability of SFHPC was not excellent above $0.75\% of the steel fiber content. Also, the compressive strength of SFHPC was decreased with increase of the steel fiber content, but the flexural strength of SFHPC was much higher than that of the concrete without the steel fiber. At the impact resistance, drop number of SFHPC for reaching final fracture was increased with increase of the fiber content. Also, the drop number for reaching initial fracture of lmm was increased with increase of the fiber content. At the sulfuric acid resistance, 4-week weight change of SFHPC with the steel fiber was almost similarity that of HPC without the steel fiber and was in the range of 73.6 to 81.5.

• 대한토목학회논문집
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• 제37권5호
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• pp.787-799
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• 2017

저수지 제체 내 수로 구조물과 흙 접촉면의 장기적인 누수가 제체 파괴의 주원인 중의 하나 임에도 불구하고 이에 대한 연구는 미미한 실정이다. 배수통관과 같은 구조물이 부분 파손되어 누수가 발생하는 경우 외형적으로 관측하기 곤란하고 파이핑 등에 의한 제체 손상 우려가 있어 이에 대한 연구가 필요하다. 본 연구는 저수지 제체를 관통하는 배수 통관이 부등침하 등으로 인해 통관 일부가 파손되어 누수가 발생하는 경우 저수지의 제체 형태를 코어형 단면과 균일형 단면으로 구분하여 수위변화에 따른 2차원 침투해석을 수행하였다. 연구결과 저수지 등의 제체를 관통하는 배수 통관으로의 누수가 발생 할 경우 통관 하부보다는 상부가 파손되어 누수가 되는 경우가 파이핑 발생 가능성이 크며, 특히 제체 하류측에서 누수가 발생하는 경우 제체 중심 코어부의 존재는 제체 안정 유지에 도움을 주고 있다고 판단된다. 또한 저수지 제체 내부 간극수압의 급격한 감소가 관측되면 파이핑 발생 우려에 대한 심도 있는 고려가 필요할 것으로 사료된다.

• 한국농공학회지
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• 제45권7호
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• pp.27-37
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• 2003

This study was performed to examine the flowing ability and filling ability of polypropylene fiber reinforced high performance concrete. The slump flow was decreased with increasing the polypropylene fiber content, rapidly. At the box-type filling ability, the difference of box height was increased with increasing the fiber content and the box-type passing ability was closed in fiber content 1 %. The final flowing distance of L-type was decreased with increasing the fiber content. Also, it was decreased above 0.75% of polypropylene fiber content, rapidly. The filling ability of L-type was badly showed above polypropylene fiber content 0.75%. Also, the compressive strength was decreased with increasing the fiber content, but the flexural strength was shown higher than that of the concrete without fiber. At the impact resistance, drop numbers for reaching in final fracture were increased with increasing the fiber content. Also, the drop numbers for reaching initial fracture of 1mm were increased with increasing the fiber content. At the acid resistance, the percent of original mass was decreased with increasing the fiber content.

• 대한기계학회논문집B
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• 제26권9호
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• pp.1218-1225
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• 2002

Large-scale vortical structure of a turbulent separation bubble affected by unsteady wake is essential to understand flow mechanisms in various fluid devices. A spoked-wheel type of wake generator provides unsteady wake, which modifies the turbulent separation bubble significantly by changing rotation directions and passing frequencies. A detailed mechanism of vortex shedding from the separation bubble with unsteady wake is analyzed by taking a conditional average with spatial box filtering, which spatially integrates measured signals at pre-determined wavelength. A convecting nature of the large-scale vortical structure is analyzed carefully. Spatial evolution of the large-scale vortical structure with frequency variance is also exemplified.

• 한국농공학회논문집
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• 제47권2호
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• pp.55-61
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• 2005

This study was performed to evaluate fluidity of super flow concrete using recycled coarse aggregate. The unit weight was $2,246{\sim}2,344\;kg/m^3$, the unit weights of these concrete were decreased with increasing the content of fly ash and recycled coarse aggregate. The slump flow was $58{\sim}63\;cm$, the Box type passing was $3.4{\sim}6.8\;cm$, respectively. The L type compacting was excellent in the fly ash content $10\%\;and\;20\%$, but, it was showed in good in the fly ash content $30\%$. The super flow concretes using recycled coarse aggregate were improved by substitution in the range of less than the fly ash content $20\%$ and recycled coarse aggregate content $75\%$. This recycled coarse aggregate can be used for super flow concrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.129-130
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• 2021

For the development of high-fluidity concrete using low-binder, The effect of the use of the developed acrylic viscosity agent on the physical properties of concrete evaluated. The amount acrylic viscosity agent used was 0.28%, 0.29% and 0.30% based on the binder amount of 350kg/m³, and slump flow test, air volume measurement, U-Box passing test and strength compressive were conducted to determine the effect of the physical properties of concrete. it was judged that 0.29% of the cellulose type viscosity agent used in high-fluidity concrete using low-binder was most suitable.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.632-637
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• 2007

The dynamic behavior of two steel bridges crossed by the Korean High Speed Train(KHST) has been investigated experimentally and the results are compared with the specification requirement of BRDM and other typical PSC Box bridge's responses. The investigated bridges are a 2-girder steel bridge of 1@40m span length(E-Won Bridge), 2@50m span length (Ji-Tan Bridge), and a PSC Box girder bridge of 2@40m span length (Yeon-Jae Bridge). A set of experimental tests were performed during operation of KHST, and a number of accelerometers, LVDTs and ring-type displacement transducers were utilized for measurement of three kinds of dynamic responses (acceleration, deflection, and end-rotation angle). Measured responses show that the vertical deflections and end-rotation angles of the three bridges are all satisfying the spec. requirement with large margin, but it was also found acceleration responses which are very close or exceed the limit value. Most of the excessive acceleration responses were found when the passing velocity of the KHST is close to the critical velocity ($V_{cr}$) which causes resonance. No noticeable differences of dynamic responses due to the different materials(steel or concrete) could be found within these experimental results.

• Structural Engineering and Mechanics
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• 제11권5호
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• pp.503-518
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• 2001

In this paper, the procedure for deriving an infinite element that is compatible with the quadrilateral Q8 element is first summarized. Enhanced by a self mesh-expansion procedure for generating the impedance matrices of different frequencies for the region extending to infinity, the infinite element is used to simulate the far field of the soil-structure system. The structure considered here is of the box type and the soils are either homogeneous or resting on a bedrock. Using the finite/infinite element approach, a parametric study is conducted to investigate the effect of open and in-filled trenches in reducing the structural vibration caused by a train passing nearby, which is simulated as a harmonic line load. The key parameters that dominate the performance of wave barriers in reducing the structural vibrations are identified. The results presented herein serve as a useful guideline for the design of open and in-filled trenches concerning wave reduction.