• Title/Summary/Keyword: Confined

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Nonlinear Analysis of Reinforced Concrete Shear Wall Using Mander's Fiber Section Analysis Method (Mander의 층상화 단면 해석방법을 이용한 철근콘크리트 전단벽체의 비선형해석)

  • Kim, Ki-Wook;Park, Moon-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.3
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    • pp.111-119
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    • 2005
  • The objective of this study is to predict fracture movements accurately and reliably by nonlinear analysis of the response of RC shear wall or RC flange sections. Hognestad's and Vallenas's theories are used for concrete model and Ramberg-Osgood's theory is used for steel model. Non-linear analysis considering confined concrete and unconfined concrete is performed. Mander's Fiber Approach Section analysis, new strain profile considering the Gamma factor are used to this section analysis. The section analysis considering cases of precracked, uncracked, boundary warping and shear warping is performed.

Structure of a single polymer chain confined in a dense array of nanoposts

  • Joo, Heesun;Kim, Jun soo
    • Proceeding of EDISON Challenge
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    • 2015.03a
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    • pp.48-52
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    • 2015
  • Control of polymer conformations in heterogeneous confinement plays an important role in natural and engineering processes. We present a simulation study on the conformational structure and dynamics of a single, flexible polymer in a dense array of nanoposts with different sizes and separations, especially, when the volume of the interstitial space formed between four nanoposts is less than the size of the polymer chain. When a polymer is placed in the array of nanoposts, the size of polymer increases compared with that in the absence of nanoposts due to the confinement effect. It is shown that when a polymer is confined in the array of nanoposts the chain is elongated in the direction parallel to the nanoposts. As the interstitial volume between four nanoposts decreases either by increasing the nanopost diameter or by decreasing the separation between nanoposts, the chain elongation becomes more pronounced. On the contrary, the polymer size varies in a non-monotonic fashion, with an initial elongation followed by a chain contraction, as the interstitial volume is reduced both by increasing the nanopost diameter and decreasing the separation at the same time while keeping constant the width of the passageway between two nanoposts. The simulation analysis shows that the non-monotonic dependence of polymer size is determined by interplay between the chain alignment along the nanoposts in each interstitial volume and the chain spreading through passageways over several interstitial volume.

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Behaviors of Hollow RC Columns with Internal Steel Tube by Hollow Ratio (강관으로 보강된 중공 RC 기둥의 중공비에 따른 거동)

  • Choi, Jun-Ho;Yoon, Ki-Yong;Han, Taek-Hee;Kang, Young-Jong
    • Journal of the Korean Society of Hazard Mitigation
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    • v.7 no.3
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    • pp.1-7
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    • 2007
  • The hollow RC(Reinforced concrete) column has the effect of reducing weight and materials compared to solid RC column. However, the hollow RC column shows a low ductile behavior due to brittle failure of inside concrete. To overcome this problem, the internally confined hollow reinforced concrete column has been developed. In this study, the behavior of internally confined hollow RC columns were evaluated with safety ratio, ductility, total material cost, the total weight of the pier, etc. The hollow ratio is varied from 0.50 to 0.85.

Effect of Surface Roughness on Two-Phase Flow Heat Transfer by Confined Liquid Impinging Jet (액체 충돌제트의 표면조도변화에 따른 이상유동 열전달 특성)

  • Yim, Seong-Hwan;Shin, Chang-Hwan;Cho, Hyung-Hee
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.8
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    • pp.714-721
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    • 2005
  • The water jet impingement cooling with boiling is one of the techniques to remove heat from high heat flux equipments. The configuration of surface roughness is one obvious condition of affecting the performance on heat transfer in nucleate boiling, The present study investigates the water jet impinging single-phase convection and nucleate boiling heat transfer for the effect of surface roughness to enhance the heat transfer in free surface and submerged jet. The distributions of the averaged wall temperature as well as the boiling curves are discussed. Jet velocities are varied from 0.65 to 1.7 m/s. Surface roughness by sand blast and sand paper varies from 0.3 to 2.51 ${\mu}m$ and cavity shapes on surface are semi-circle and v-shape, respectively The results showed that higher velocity of the jet caused the boiling incipience to be delayed more. The incipient boiling and heat transfer increase with increasing surface roughness due to a large number of cavities of uniform size.

Analytical model for high-strength concrete columns with square cross-section

  • Campione, G.
    • Structural Engineering and Mechanics
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    • v.28 no.3
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    • pp.295-316
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    • 2008
  • In the present paper a mechanical model to predict the compressive response of high strength short concrete columns with square cross-section confined by transverse steel is presented. The model allows one to estimate the equivalent confinement pressures exercised by transverse steel during the loading process taking into account of the interaction of the stirrups with the inner core both in the plane of the stirrups and in the space between two successive stirrups. The lateral pressure distributions at hoop levels are obtained by using a simple model of elastic beam on elastic medium simulating the interaction between stirrups and concrete core, including yielding of steel stirrups and damage of concrete core by means of the variation in the elastic modulus and in the Poisson's coefficient. Complete stress-strain curves in compression of confined concrete core are obtained considering the variation of the axial forces in the leg of the stirrup during the loading process. The model was compared with some others presented in the literature and it was validated on the basis of the existing experimental data. Finally, it was shown that the model allows one to include the main parameters governing the confinement problems of high strength concrete members such as: - the strength of plain concrete and its brittleness; - the diameter, the pitch and the yielding stress of the stirrups; - the diameter and the yielding stress of longitudinal bars; - the side of the member, etc.

FE modeling of Partially Steel-Jacketed (PSJ) RC columns using CDP model

  • Ferrotto, Marco F.;Cavaleri, Liborio;Trapani, Fabio Di
    • Computers and Concrete
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    • v.22 no.2
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    • pp.143-152
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    • 2018
  • This paper deepens the finite element modeling (FEM) method to reproduce the compressive behavior of partially steel-jacketed (PSJ) RC columns by means of the Concrete Damaged Plasticity (CDP) Model available in ABAQUS software. Although the efficiency of the CDP model is widely proven for reinforced concrete columns at low confining pressure, when the confinement level becomes high the standard plasticity parameters may not be suitable to obtain reliable results. This paper deals with these limitations and presents an analytically based strategy to fix the parameters of the Concrete Damaged Plasticity (CDP) model. Focusing on a realistic prediction of load-bearing capacity of PSJ RC columns subjected to monotonic compressive loads, a new strain hardening/softening function is developed for confined concrete coupled with the evaluation of the dilation angle including effects of confinement. Moreover, a simplified efficient modeling approach is proposed to take into account also the response of the steel angle in compression. The prediction accuracy from the current model is compared with that of existing experimental data obtained from a wide range of mechanical confinement ratio.

Preparation of Gallium Nitride Powders and Nanowires from a Gallium(III) Nitrate Salt in Flowing Ammonia

  • Jung, Woo-Sik
    • Bulletin of the Korean Chemical Society
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    • v.25 no.1
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    • pp.51-54
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    • 2004
  • Gallium nitride (GaN) powders were prepared by calcining a gallium(III) nitrate salt in flowing ammonia in the temperature ranging from 500 to 1050 $^{\circ}C$. The process of conversion of the salt to GaN was monitored by X-ray diffraction and $^{71}Ga$ MAS (magic-angle spinning) NMR spectroscopy. The salt decomposed to ${\gamma}-Ga_2O_3$ and then converted to GaN without ${\gamma}-{\beta}Ga_2O_3$ phase transition. It is most likely that the conversion of ${\gamma}-Ga_2O_3$ to GaN does not proceed through $Ga_2O$ but stepwise via amorphous gallium oxynitride ($GaO_xN_y$) as intermediates. The GaN nanowires and microcrystals were obtained by calcining the pellet containing a mixture of ${\gamma}-Ga_2O_3$ and carbon in flowing ammonia at 900 $^{\circ}C$ for 15 h. The growth of the nanowire might be explained by the vapor-solid (VS) mechanism in a confined reactor. Room-temperature photoluminescence spectra of as-synthesized GaN powders obtained showed the emission peak at 363 nm.

Numerical investigation on the performance of the aluminized HMX with varying aluminum concentration (알루미늄 함유량 변화에 따른 알루미늄 입자가 함유된 HMX 성능에 관한 수치 연구)

  • Kim, Wuhyun;Gwak, Min-cheol;Yoh, Jai-ick
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.617-621
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    • 2017
  • The performance characteristics of aluminized high explosive are considered by varying the aluminum(Al) concentration in a two-phase model. Since the time scales of the characteristic combustion process of high explosives and Al particles differ, the process of energy release behind the leading detonation wave front occurs over an extended period of time. Two cardinal observations are reported: a decrease in detonation velocity with an increase in Al concentration and a double front detonation (DFD) feature when anaerobic Al reaction occurs behind the front. In the current study, a series of confined rate sticks are considered for characterizing the performance of aluminized HMX with a maximum Al concentration of 50%. The simulated results are compared with the experimental data for 5%-25% concentrations.

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Surface Plasmon Modes Confined in the Gap Between Metal Nanowire and Dielectric Slab (유전체 판과 금속 나노선 사이에 구속된 표면 플라즈몬 모드)

  • Hahn, Chol-Oong;Oh, Cha-Hwan;Song, Seok-Ho
    • Korean Journal of Optics and Photonics
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    • v.22 no.6
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    • pp.269-275
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    • 2011
  • We propose a metal-dielectric hybrid waveguide structure consisting of a single metal nanowire placed on a flat dielectric slab. Mode size and propagation loss of the surface-plasmons confined in the metal-dielectric gap are compared with those of the complementary structure with a dielectric nanowire on a metal surface. In the case of the nanowire's diameter much smaller than the wavelength the two structures reveal quite different characteristics; the dielectric nanowire-on-metal has longer propagation distance, but only the metal nanowire-on-dielectric exhibits a mode size two fold smaller than the diffraction limit. The proposed hybrid structure may therefore be more suitable for realization of nanocavity lasers.

A Study on the Hydrodynamic Force Acting on a Large Vessel in the Proximity of Breakwater (방파제 형상 연직구조물 부근을 항행하는 대형선박에 미치는 간섭력에 관한 연구)

  • Lee, Chun-Ki
    • Journal of Navigation and Port Research
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    • v.37 no.4
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    • pp.345-350
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    • 2013
  • It is well known that the hydrodynamic forces and moments induced by the proximity of bank in confined waters, such as in a harbour or narrow channel affect ship's maneuvering motion. In this paper, the calculation method based on the slender body theory for estimation of the hydrodynamic force between ship and breakwater is applied, and also, the characteristic features of hydrodynamic force acting on a large vessel in the proximity of a breakwater are described and illustrated. Furthermore, the effects of water depth and the lateral spacing between ship and breakwater are summarized and discussed.