• 한국강구조학회 논문집
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• 제15권2호
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• pp.207-217
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• 2003

콘크리트충전 강관구조는 합성효과에 의해 강관과 콘크리트의 단점을 상호보완하여 역학적으로 우수한 성능을 발휘할 수 있다. 그래서, 최근에는 고층건물에 구조시스템의 대안으로서 주목을 받고 있다. 본 연구의 목적은 일정축력과 반복 수평력을 받는 콘크리트충전 강관기둥의 내력 및 변형성능을 평가하는 것이다. 이 실험의 변수로는 강관의 폭두께비, 축력비 및 강관의 형상으로 정하여 총 18개의 실험체를 제작하여 실험하였다. 실험결과로부터 실험체의 최대내력 및 변형성능에 대해 검토하였다.

• 대한기계학회논문집A
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• 제33권10호
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• pp.1108-1118
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• 2009

A Very High Temperature Gas Cooled Reactor (VHTR) has been selected as a high energy heat source of the order of $950^{\circ}C$ for nuclear hydrogen generation, which can produce hydrogen from water or natural gas. A primary hot gas duct (HGD) as a coaxial double-tube type cross vessel is a key component connecting a reactor pressure vessel and an intermediate heat exchanger in the VHTR. In this study, a structural sizing methodology for the primary HGD of the VHTR is suggested in order to modulate a flow-induced vibration (FIV). And as an example, a structural sizing of the horizontal HGD with a coaxial double-tube structure was carried out using the suggested method. These activities include a decision of the geometric dimensions, a selection of the material, and an evaluation of the strength of the coaxial double-tube type cross vessel components. Also in order to compare the FIV characteristics of the proposed design cases, a fluid-structure interaction (FSI) analysis was carried out using the ADINA code.

• 한국강구조학회 논문집
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• 제13권2호
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• pp.201-210
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• 2001

본 연구에서는 편심 축력을 받는 가셋트-강관 접합부의 극한 내력을 파악하기 위하여 실험 및 유한요소해석을 수행하였다. 가셋트-강관 접합부의 내력에 영향을 주는 요소는 강관의 직경, 가셋트판 길이, 축력과 횡력의 비, 횡력에 의한 편심 등으로 이들이 주재의 좌굴내력에 미치는 영향을 정량적으로 파악하여 접합부 강도식을 제안하였다. 특히 횡력에 의한 편심이 주재에 작용할 때 이를 설계식에 반영하기 위하여 횡력을 등가의 모멘트 및 편심 축력으로 대치한 수치 모형을 제시하였다. 결과적으로 접합부의 작용하는 외력을 주주재 축력, 모멘트, 편심 축력으로 분해하고 각 외력에 대한 독립적인 극한내력을 구한후 이들의 상관 관계식을 구함으로써 접합부 극한강도식을 제시하였다.

• 한국강구조학회 논문집
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• 제9권1호통권30호
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• pp.121-128
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• 1997

It has been reported by the existing papers that the ultimate load capacity and energy absorption capacity of the CFST column are considerably higher than those resulting from a simple addition of the capacities of the concrete and the steel tube. It is normally believed that the confined effect for the infilled concrete due to the hoop tension of steel at the parameter of cross sections can remarkably improve the ductility and energy absorption capacities of the CFST columns. This paper provides the results of a study on the load-carrying capacities and energy absorption capacities of the CFST columns, a numerical analysis method, i. e. N-M interaction curves and Moment curvature relationships. The numerical approaches are verified by comparing with the existing test results and the circular and square steel tube sections are selected to clarify the amount of confinement effects to improve the ultimate deformable capacity(a ultimate strain value) of the infilled concrete. Then, an adequate value of the ultimate strain of the infilled concrete and an equation of the ultimate capacity of the CFST column are suggested.

• Corrosion Science and Technology
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• 제8권3호
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• pp.126-131
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• 2009

The interaction between wear and corrosion can significantly increase total material losses in water chemistry environment. The corrosive wear tests of a PWR steam generator tube material (Alloy 690) against the anti vibration bar material (409 SS) were performed at room temperature. The tests were performed in alkaline water chemistry conditions. NaOH solution was selected for test condition to investigate the corrosive wear effect of steam generator tube material in alkaline pH condition without other factors. The flow induced vibration can caused tube damage and the corrosion can be occurred by water chemistry. The test results showed that, in the alkaline solution at pH 13.9, the corrosion current density was increased about ten times than that in the distilled water. And wear rate at pH 13.9 was increased about ten times from that at neutral condition. However, the wear rate was decreased with time. The decrease would be attributed to the change in roughness of specimen or sub-layer of the worn surface with time. From microstructure observation, severe abrasive shape and several wear debris were found. From those results, it could infer that the oxide film on Alloy 690 changed to easily breakable one in the alkaline water, and then abrasion with corrosion became the main wear mechanism.

• 한국콘텐츠학회논문지
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• 제20권2호
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• pp.114-126
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• 2020

정보통신기술의 발달로 이용자들은 모바일을 통해 시간과 공간의 제약 없이 동영상 콘텐츠를 즐길 수 있게 되었다. 본 연구에서는 이용과 충족 이론을 활용하여 유튜브 이용자들의 이용 동기와 친밀도가 이용자 활동에 미치는 영향을 살펴보고자 한다. 특히 본 연구는 기존 연구들과 달리 이용자 활동을 시청 전과 동안 활동으로 나누어 살펴보았다. 연구결과 시청 전 활동인 구독채널 수에 영향을 미치는 주요 동기는 유용한 즐거움과 사회적 상호작용인 것에 비해, 시청 동안 활동에 영향을 미치는 주요 동기는 유용한 즐거움, 사회적 상호작용, 인간관계 연결, 유용한 정보탐색, 공동시청과 같이 더욱 다양하게 나타났다. 또한 유튜브에 대한 친밀감도 시청행동에 유의미한 영향을 미치는 것으로 나타났다. 결론에서 결과에 대한 이론적 및 실무적 함의가 논의되었다.

• 한국강구조학회 논문집
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• 제8권4호통권29호
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• pp.59-76
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• 1996

Concrete filled steel tube column has a large load carrying capacity through its steel and concrete interaction which makes it useful in construction. However, it has not been used often in a practical construction field. This is partly due to the non-destructive inspection method for concrete filling which has yet to be established. Furthermore, there are the lack of test data and a practical method in evaluating the ultimate load carrying capacity of concrete filled steel tube column. This paper will attempt to predict the ultimate strength of short concrete filled square tubular steel columns through conducting several tests. To accumulate the new test data on concrete filled steel tube columns, a total of 42 specimens of steel tubular columns were monotonically tested under concentric axial force, having the slenderness ratio(${\lambda}=10,\;15,\;20$), width-thickness ratio(d/t=25.0, 33.3) and concrete strengths($F_{c}=210,\;240,\;270kg/cm^{2}$). The hollow sections and concrete filled steel columns were compared to check the lateral confinded effects by steel tube. Through these test results, we propose a coefficient k=3.64 for the strength evaluation formula(10) of concrte filled tubular steel short columns.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1255-1260
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• 2006

To maintain the structural integrity of steam generator tubes, 40% of wall thickness plugging criterion has been developed. The approach is for the steam generator tube with single crack, so that the interaction effect of multiple cracks can not be considered. Although, recently, several approaches have been proposed to assess the integrity of steam generator tube with two identical cracks whilst actual multiple cracks reveal more complex shape. In this paper, the coalescence pressure of steam generator tube containing multiple cracks of different length is evaluated based on the detailed 3-dimensional (3-D) elastic-plastic finite element (FE) analyses. In terms of the crack shape, two collinear axial through-wall cracks with different length were considered. Furthermore, the resulting FE coalescence pressures are compared with FE coalescence pressures and experimental results for two identical collinear axial through-wall cracks to quantify the effect of crack length ratio on failure behavior of steam generator tube with multiple cracks. Finally, based on 3-D FE results, the coalescence evaluation diagrams were proposed.

• 설비공학논문집
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• 제7권4호
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• pp.589-599
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• 1995

The frictional pressure drop of a capillary tube flow is experimentally investigated for pure refrigerants such as R32, R125, and R134a and refrigerant mixtures such as R32/R134a(30/70 by mass percent), R32/R125(60/40), R125/R134a(30/70), and R32/R125/R134a(23/25/52). The binary interaction parameters for the calculation of viscosities of refrigerant mixtures are found based upon the data in the open literature. Several homogeneous flow models predicting the viscosity of two-phase region are compared to select the best model. Cicchitti's equation is known to be the most adequate for the prediction of the viscosity for refrigerant mixtures, which is used in the analysis of adiabatic capillary flows. A model for the prediction of the frictional pressure drop of single and two-phase flow is developed for refrigerant mixtures in this study. This model may be used to design and analyze the performance of a capillary tube in the refrigerating system.

• Steel and Composite Structures
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• 제31권3호
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• pp.291-301
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• 2019

Pure torsion loading conditions were not frequently occurred in practical engineering, but the torsional researches were important since it's the basis of mechanical property researches under complex loading. Then a 3D finite element model with precise material constitutive models was established, and the effectiveness was verified with test data. Parametric studies with varying factors as steel yield strength, concrete strength and sectional height-width ratio, were performed. Internal stress state and the interaction effect between encased steel tube and the core concrete were analyzed. Results indicated that due to the confinement effect between steel tube and core concrete, the torsional strength of CFT columns was greatly improved comparing to plain concrete columns. The steel ratio would greatly influence the torque share between the steel tube and the core concrete. Then the torsional strength calculation formulas for core concrete and the whole CFT column were proposed. The proposed formula could be simpler and easier to use with guaranteed accuracy. Related design codes were more conservative than the proposed formula, but the proposed formula presented more satisfactory agreement with experimental results.