• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.365-368
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• 2006

RBSN Method, Rigid-Body-Spring Network Method, is a structural analysis method that overcomes the problems faced in FEM analysis of concrete or crack forming structures. In RBSN, irregular lattices are used to model structural components consisting of bulk material, curvilinear reinforcements, and their interfaces. Because reinforcements and their interfaces in the bulk material are freely positioned, meshing is irrespective of the geometry of the representing bulk material. In this paper, RBSN method of 3D is applied in simulating the pull-out test of FRP (Fiber Reinforced Polymer) embedded in concrete. The comparison of analysis results to experimental results shows that RBSN method simulates the shear-slip behavior very precisely. From the analysis results, 3D RBSN method is proven to be an effective and accurate analysis method for concrete structural analysis. Also, the results show that RBSN method can be a potential analysis method for concrete structures that can replace the current FEM analysis.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3741-3746
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• 2012

불충분한 시인성에 기인한 안전사고가 연안지역에 많이 발생되고 있다. 그러므로 이러한 안전사고를 방지하기 위하여 시인성을 겸비한 안전시설이 요구되고 있다. 이와 같은 요구사항을 해결하기 위하여 본 연구에서는 발광체 인입형 콘크리트(LESeCON)의 개념을 정립하고 이를 이용하여 연안지역에 적용하기 위한 콘크리트 경계블록을 개발 및 제작하였다. 개발된 콘크리트 경계블록의 역학적 및 기능적 성능을 검증하기 위하여 휨강도 실험과 시인성 실험을 실시하였다.

• 대한치과보철학회지
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• 제42권5호
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• pp.535-543
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• 2004

Purpose: The purpose of this study is to compare the effect of two fiber post systems and one metal cast post system on the fracture strength and fracture pattern of crowned, endodontically treated teeth with 2 mm-height of the reamining tooth structure. Materials and methods: A total of 36 recently extracted sound human mandibular premolars were selected Each tooth structure of the crown portion except 2mm-height of the one above the cementoenamel junction was removed. After being endodontically treated, they were randomly distributed into 3 groups: group 1, restored with quarts fiber post(D.T. Light-Post), group 2, with glass fiber post(FRC Postec), and group 3, metal cast post and core. All teeth were fully covered with nonprecious metal crowns. Each specimen was embedded in an acrylic resin block and then secured in a universal load-testing machine. A compressive load was applied at a 130 degree angle to the long axis of the tooth until fractured, at a crosshead speed 20mm/min. The highest fracture loads were measured and recorded as the fracture strength of each specimen. Fracture areas were measured on the mid-buccal and mid-lingual point from the crown margins. One-way analysis of variance and Turkey test were used to determine the statistic significance of the different fracture loads and areas among the groups (p<0.05). Results: The mean fracture loads were $1391{\pm}$425N(group 1), $1458{\pm}476N$(group 2) and $1301{\pm}319N$(group 3). The fracture loads among the three groups had no statistically signifiant difference (p>.05). The mean fracture area of the fiber post was closer to the crown margin than that of the metal cast post and core(p<.05). The metal cast post showed unrestorable and catastrophic fracture patterns. Conclusion: Within the limitations of this study, fracture loads with any statistically significant difference were not recorded for endodontically treated teeth restored with two fiber posts and the metal cast post. But teeth restored with the fiber posts typically showed the fracture pattern close to the crown margin, which was almost restorable.

• 접착 및 계면
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• 제12권3호
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• pp.88-93
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• 2011

페놀수지에 함침된 탄소나노튜브 (CNT)의 최적 분산제조공정은 전기저항 측정으로 구해졌으며, 플라즈마 처리된 탄소섬유와 CNT-페놀수지 나노복합재료간의 계면특성이 전기-미세역학시험법에 의해 연구되었다. 탄소섬유의 젖음성은 플라즈마 처리 후에 현격하게 증가되었다. 탄소섬유와 CNT-페놀수지 나노복합재료의 표면에너지는 Wilhelmy 플레이트 시험법으로 측정되었다. 탄소섬유 표면의 활성화로 인하여 플라즈마 처리 후 전진 접촉각은 $65^{\circ}$에서 $28^{\circ}$로 감소되었다. 이는 정적 접촉각과 상호 일치함을 보여 주었다. 플라즈마 처리된 탄소섬유와 CNT-페놀수지 나노복합재료간의 접착일은 플라즈마 처리전보다 증가하였다. 또한, 계면전단강도와 겉보기 강성도 탄소섬유에 대한 플라즈마 처리로 증가하였다.

• International Journal of Concrete Structures and Materials
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• 제18권1E호
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• pp.29-34
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• 2006

Elastic modulus, tensile and bond capacities are important factors for developing an effective reinforcing action of a flexural member as a reinforcing material for concrete structures. Reinforcement must have enough bond capacity to prevent the relative slip between concrete and reinforcement. This paper presents an experimental study to clarify the bond capacity of prestressed carbon fiber reinforced polymer(CFRP) rod manufactured by an automatic assembly robot. The bond characteristics of CFRP rods with different pitch of helical wrapping were analyzed experimentally. As the result, all types of CFRP rods show a high initial stiffness and good ductility. The mechanical properties of helical wrapping of the CFRP rods have an important effect on the bond of these rods to concrete after the bond stress reached the yield point. The stress-slip relationship analyzed from the pull-out test of embedded cables within concrete was linear up to maximum bond capacity. The deformation within the range of maximum force seems very low and was reached after approximately 1 mm. The average bond capacity of CF20, CF30 and CF40 was about 12.06 MPa, 12.68 MPa and 12.30 MPa, respectively. It was found that helical wrapping was sufficient to yield bond strengths comparable to that of steel bars.

• Geomechanics and Engineering
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• 제2권2호
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• pp.89-106
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• 2010

Sliding within the dam foundation is one of the key failure modes of a gravity dam. A two-dimensional (2-D) physical model test has been conducted to study the sliding failure of a concrete gravity dam under overloading conditions. This model dam was instrumented with strain rosettes, linear variable displacement transformers (LVDTs), and embedded fiber Bragg grating (FBG) sensing bars. The surface and internal displacements of the dam structure and the strain distributions on the dam body were measured with high accuracy. The setup of the model with instrumentation is described and the monitoring data are presented and analyzed in this paper. The deformation process and failure mechanism of dam sliding within the rock foundation are investigated based on the test results. It is found that the horizontal displacements at the toe and heel indicate the dam stability condition. During overloading, the cracking zone in the foundation can be simplified as a triangle with gradually increased height and vertex angle.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.159.2-159.2
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• 2010

Asbestos is the collective name for a group of naturally occurring minerals in their fibrous form and hydrous silicates of magnesium and a mineral fiber that has been used commonly in a variety of building construction materials for insulation and as a fire-retardant. Asbestos has been used for a wide range of manufactured goods, because of its fiber strength and heat resistant properties. Nevertheless harmful of asbestos is quite serious. Exposure to airborne friable asbestos may result in a potential health risk because persons breathing the air may breathe in asbestos fibers. Continued exposure can increase the amount of fibers that remain in the lung. Fibers embedded in lung tissue over time may cause serious lung diseases including asbestosis, lung cancer. In this paper, we carried out as fundamental study for dispose of asbestos cement slate safely and perfectly. Melting Temperature of asbestos need to more than $1,520^{\circ}C$ and specially asbestos cement slate need more energy than that of pure asbestos. We need to decrease melting temperature of asbestos cement slate for economical efficiency. To the purpose, glass and bottom ash were chosen as additives for basicity control. we analyzed about properties of asbestos cements slate, melting characteristics on the additives ratio and temperature. We confirmed about harmlessness of melting slag through analysis of scanning electron microscope(SEM) and x-ray diffractometer(XRD).

• Composites Research
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• 제18권5호
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• pp.15-20
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• 2005

본 논문에서는 복합재 파손에 의한 음향방출해석을 3차원 유한요소법과 외연시간적분법을 이용하여 구현하였다. 음원모델은 등가체적력 모델을 사용하였다. 계산기법의 타당성을 검증하기 위해 단일 섬유가 내재된 등방성 평판에서 섬유파손 시 발생하는 탄성파에 의한 동적변위를 시험과 비교하였다. 적층 복합재의 경우, 섬유와 기지를 각기 모델링한 방법과 균질화한 모델을 비교하여 차이점을 비교하였다. 음향방출에서 발생하는 고주파 성분을 검출하기 위해 계산시간 스텝이 매우 작아야 하며, 매우 많은 자유도의 모델이 동반되어야 한다. 이러한 대규모 문제를 효과적으로 해결하기 위해 병렬 계산 기법을 도입하였다.

• Smart Structures and Systems
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• 제22권1호
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• pp.1-11
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• 2018

This study presents early crack detection of steel fiber-reinforced concrete (SFRC) under varying temperature and humidity conditions using an instantaneous electrical impedance acquisition system. SFRC has the self-sensing capability of electrical impedance without sensor installation thanks to the conductivity of embedded steel fibers, making it possible to effectively monitor cracks initiated in SFRC. However, the electrical impedance is often sensitively changed by environmental effects such as temperature and humidity variations. Thus, the extraction of only crack-induced feature from the measured impedance responses is a crucial issue for the purpose of structural health monitoring. In this study, the instantaneous electrical impedance acquisition system incorporated with SFRC is developed. Then, temperature, humidity and crack initiation effects on the impedance responses are experimentally investigated. Based on the impedance signal pattern observation, it is turned out that the temperature effect is more predominant than the crack initiation and humidity effects. Various crack steps are generated through bending tests, and the corresponding impedance damage indices are extracted by compensating the dominant temperature effect. The test results reveal that propagated cracks as well as early cracks are successfully detected under temperature and humidity variations.

• International Journal of Automotive Technology
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• 제7권5호
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• pp.555-564
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• 2006

The aim of this paper is to contribute to the efficient design of traffic light poles involved in vehicle frontal collisions by developing a computer-based, finite-element model capable of capturing the impact characteristics. This is achieved by using the available non-linear dynamic analysis software "LS-DYNA3D", which can accurately predict the dynamic response of both the vehicle and the traffic light pole. The fiber reinforced polymer(FRP) as a new pole's material is proposed in this paper to increase energy absorption capabilities in the case of a traffic pole involved in a vehicle head-on collision. Numerical analyses are conducted to evaluate the effects of key parameters on the response of the pole embedded in soil when impacted by vehicles, including: soil type(clay and sand) and pole material type(FRP and steel). It is demonstrated from the numerical analysis that the FRP pole-soil system has favorable advantages over steel poles, where the FRP pole absorbed vehicle impact energy in a smoother behavior, which leads to smoother acceleration pulse and less deformation of the vehicle than those encountered with steel poles. Also, it was observed that clayey soil brings a slightly more resistance than sandy soil which helps reducing pole movement at ground level. Finally, FRP pole system provides more energy absorbing leading to protection during minor impacts and under service loading, and remain flexible enough to avoid influencing vehicle occupants, thus reducing fatalities and injuries resulting from the crash.