• Journal of the Korean Society of Visualization
• /
• v.3 no.1
• /
• pp.20-25
• /
• 2005

An x-ray PIV (Particle Image Velocimetry) technique was developed fur measuring quantitative information on flows inside opaque conduits and/or opaque-fluid flows. To check the performance of the x-ray PIV technique developed, it was applied to a liquid flow in an opaque Teflon tube. To acquire x-ray images suitable for PIV velocity field measurements, the refraction-based edge enhancement mechanism was employed with seeding detectable tracer particles. The amassed velocity field data obtained were in a reasonable agreement with the theoretical prediction. The x-ray PIV technique was also applied to get velocity fields of blood flow and to measure size and velocity of micro-bubbles simultaneously, and to visualize the water refilling process in bamboo leaves. The x-ray PIV was found to be a powerful transmission-type flow imaging technique fur measuring quantitative information of flows inside opaque objects and various opaque-fluid flows.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.6
• /
• pp.11-15
• /
• 2009

Recently, a new PSC (Prestressed Concrete) bridge system, which is supported by Concrete-filled fiber-reinforced polymer (CFFRP) strut, has been introduced. This bridge is able to reduce self-weight and increase the width of traditional PSC bridges. However, no relevant research has been reported on local behavior of CFFRP strut in the bridge system. The purpose of this study is to investigate local behavior of CFFRP struts using fiber Bragg grating (FBG) sensors. Field tests were performed to examine the hoop strains and longitudinal strains of the FRP strut under various lateral positions and velocities of a test truck. It has been observed that CFFRP strut is under compression regardless of vehicle speed and location. However, the CFFRP strut is sensitive to the lateral position of vehicles in terms of strain magnitude. Results also indicated that the FBG sensors can faithfully record the hoop and longitudinal strains of the FRP strut without electro-magnetic interference.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.9
• /
• pp.27-33
• /
• 2011

In the case of the existing method of underground pipe construction, the difficulty of the bedding compaction of pipe causes reducing the compaction efficiency and the stability of the underground facilities and conclusively damaging the structures. One of the methods to solve these problem is using the flowable fills as a backfill material. Therefore, in this study, numerical analysis of the underground pipe was performed in order to evaluate the behavior of pipe according to backfill mixtures. To estimate the deformation characteristic of the underground pipe, the displacement of the main part of the pipe, ground settlement and vertical earth pressures were measured in different backfill mixtures and maintaining the other conditions constantly. As a result of numerical analysis, using the flowable fills as the backfill material is better than using sand in reducing the ground settlement, the pipe deformation and the vertical earth pressure aspect.

• Journal of Energy Engineering
• /
• v.27 no.4
• /
• pp.64-69
• /
• 2018

The purpose of this study is to expand the use of coal ash and coal slag in thermal power plants. In addition, controlled low strength materials was developed to prevent mine settlement. Bottom ash and KR slag are mixed at ratio of 7:3 to expand the use of industrial by-products through carbonate reaction and inhibit the exudation of heavy metals. In order to efficiently fill the abandon mine, workability and physical properties were evaluated according to flow. As a result of elution of harmful substance experiment, it was confirmed that the carbonation reaction inhibited the elution of heavy metals. It was confirmed that the difference in water ratio was the difference in specific surface area of the controlled low strength materials. It was confirmed that the working efficiency is excellent when the flowability is 300mm compared to 260mm. compressive strength measurement result was relatively high at 260mm compared to 300mm because the number of pores due to decrease of water ratio was small.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.11a
• /
• pp.18.1-18.1
• /
• 2009

금속 다공체는 자동차, 선박, 건축 등의 분야에서 구조물이나 충격흡수제 등으로 응용되고 있는데 이들은 일반 금속 구조물에 비해 가볍고 플라스틱에비해서는 강한 장점을 지닌다. 현재 사용되고 있는 대부분의 금속 다공체는 발포 주조공정으로 제조된 알루미늄으로서, 철계 합금에 비해 가벼운 장점을 갖지만 강도가 상당히 떨어지고 가격이 높은 단점을 가진다. 따라서 본 연구에서는 알루미늄 대신 철계 합금으로 다공체를 제조하고자 하였고 제조방법으로는 주조공정 대신 분말공정을선택하였다. 분말공정은 구형 스티로폼을 금속분말 슬러리로 코팅한 후 스티로폼을 제거하여 낱개의 금속중공체(Metallic Hollow Sphere)를 제조하고 이렇게 제조된 중공체를 뭉쳐 성형함으로써최종 형상의 다공체를 제조하는 방법이다. 이 방법으로 제조된 다공체는 주조공정으로 제조된 다공체보다높은 강도를 나타내며 낱개의 중공체는 성형공정을 거치지 않고 필터나 충진재 등의 새로운 용도로 활용될 수 있다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.04a
• /
• pp.211-214
• /
• 2003

본 연구는 운동장, 주차장, 도로측면, 보도, 기타 주거시설 등의 우수 차집시설에 사용되는 콘크리트 구조물의 침투능 확보를 위한 투수성 차집구조물 개발에 관한 것이다. 일반적인 차집시설(측구, 받이, 맨홀등)을 투수가 가능한 구조로 변경하여 우수의 침투를 발생시킴으로서 우수유출을 저감하고 지하수론 확보할 수 있다. 투수성을 확보하기 위하여 일반 차집시설의 콘크리트 구조체 벽면에 천공을 하고 천공된 측구내에 쇄석을 충진시켜 침투되는 우수의 수질도 개선할 수 있다. 본 제작방법은 별도의 침투소재를 사용하는 경우와 비교해 볼 때 경제성이 우수하며 동일시공방법과 규격으로 대체재로서 활용성이 높을 것으로 전망된다.

• Proceedings of the KAIS Fall Conference
• /
• 2005.05a
• /
• pp.321-323
• /
• 2005

중수숭급기 충진재의 부식원인인 염분 유입 및 열분해로 인한 산화물 형성 과정 조사를 위해 zeolite 의 열분해 및 염분 유입을 조사하였다. 그리고 원자력 발소의 dryer 모사 장치를 만들어 열분해 특성 조사 실험을 하였다. zeolite 열분해 특성 조사 결과 zeolite에 고온의 증기를 통과시키면 가수분해가 일어나 구조가 바뀌게 되며, $500\~700^{\circ}C$에서 완전히 열분해 된다. 그리고 열분해가 일어난 zeolite에 염분이 유입되면, zeolite의 $H^+$와 염분의 $Na^+$ 가 자리바꿈을 하게 되고, 수중에 $H^+$ 와 $Cl^-$ 가 존재하여 HCl이 형성될 것으로 조사되었고, 실험 결과 pH가 4.5, 4.53, 4.72, 4.64, 4.86, 5.03, 4.61로 낮게 측정되었다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.1
• /
• pp.1-8
• /
• 2012

This study is a basic experimental research to apply FRP (Fiber Reinforced Polymer) box members to slabs and girders among various architectural structures, which receive bending stress. We prepared prefabricated FRP member and connected it to an FRP box member as a large cross section before we conducted an experiment in diverse conditions to analyze characteristics of compressive fracture behavior. In this study, we carried out a compressive fracture behavior test according to fillers on the upper part of the FRP box member, loading methods, and connective types and thereby performed a finite element analysis. The comparison of analysis results with test results revealed that rigidity was found to be slightly low, while stress was concentrated on the fracture point of the sample.

• Journal of the Korea Concrete Institute
• /
• v.20 no.1
• /
• pp.59-66
• /
• 2008

This study is about manufacturing and producing girder, which is an essential component of bridge structure, in a composite of FRP + concrete. This has a higher competitive power in price than steel girder. The girder used in this study is made of glass fiber which has a lower elastic modulus than steel and thus has some technical limitations such as excessive deflection compared to steel girder and lack of production facilities in FRP production companies to make a large-section component material. Thus, this study suggested a section of a new module that will allow for applying a large section in order to solve the technical difficulties mentioned above and to secure low stiffness of FRP, developed a new FRP+concrete composite girder that is filled with the appropriate amount of concrete. To identify the structural behavior of this FRP+concrete composite girder, experiments were conducted to measure its flexural strength according to the difference in the strength of confined concrete and the existence of stud. The results of the flexural strength test confirmed the composite effect from confining concrete and the effect of increase in strength proportional to the strength of concrete. In developing FRP+concrete composite girder, NDT study was also conducted to analyze the interface characteristics of concrete and FRP.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.28 no.2
• /
• pp.27-34
• /
• 2024

This study was conducted to examine the feasibility of using Fe-activated wood-derived biochar as a conductive filler for manufacturing cement-based strain sensor. To evaluate the compressive and electrical properties of cement composite with 3% Fe-activated biochar, three cubic specimens of size 50 x 50 x 50mm³ and three prismatic cement-based sensors of size 40 x 40 x 80mm³ were prepared respectively. The four-probe method of electrical resistance measurement was used for cement-based sensors. For cement-based sensors with FE-activated biochar, the conductive performance such as electrical resistance and impedance under different water content and repeated compression was investigated. Results showed that the fractional changes in the DC electrical resistivity of cement-based sensors increase with increasing time and the maximum fractional changes in the resistivity decrease with increasing the moisture contents during 900s. At moisture content of 7.5% range, the conductive performance of cement composite including 3% Fe-activated biochar as a conductive filler showed the most stable, while the strain detection ability tended to decrease somewhat as the repeated compressive stress increased between repeated compressive strain and fractional change in resistivity (FCR).