• Title, Summary, Keyword: range of confinement

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Constitutive Model of Laterally Confined High Strength Concrete (횡구속된 고강도 콘크리트의 구성모델)

  • Yun, Sung-Hwan;Kang, Yoon-Sig;Park, Tae-Hyo
    • Journal of the Korea Concrete Institute
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    • v.22 no.4
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    • pp.481-488
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    • 2010
  • Since existing constitutive models developed for confined normal strength concrete overestimate ductility when they are applied to confined high strength concrete, these models cannot be directly applied to confined high strength concrete. In an effort to solve this problem, an accurate stress-strain relationship of the hihg strength concrete needs to be formulated by examining the confinement effects due to increase of the concrete strength. In this study, a constitutive model is developed to express the stress-strain relationship of confined high strength concrete by carrying out regression analysis of the main parameters affection strength and ductile behavior of reinforced high strength concrete columns. Twenty-five test specimens were chosen from the reported experimental studies in the literature. The experimental results of stress-strain relationships of show a good agreement with results of the stress-strain relationships of suggested high strength concrete, covering a strength range between 60 and 124 MPa.

Tests and mechanics model for concrete-filled SHS stub columns, columns and beam-columns

  • Han, Lin-Hai;Zhao, Xiao-Ling;Tao, Zhong
    • Steel and Composite Structures
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    • v.1 no.1
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    • pp.51-74
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    • 2001
  • A series of tests on concrete-filled SHS (Square Hollow Section) stub columns (twenty), columns (eight) and beam-columns (twenty one) were carried out. The main parameters varied in the tests are (1) Confinement factor (${\xi}$) from 1.08 to 5.64, (2) concrete compression strength from 10.7MPa to 36.6MPa, (3) tube width to thickness ratio from 20.5 to 36.5. (4) load eccentricity (e) from 15 mm to 80 mm and (5) column slenderness (${\lambda}$) from 45 to 75. A mechanics model is developed in this paper for concrete-filled SHS stub columns, columns and beam-columns. A unified theory is described where a confinement factor (${\xi}$) is introduced to describe the composite action between the steel tube and filled concrete. The predicted load versus axial strain relationship is in good agreement with stub column test results. Simplified models are derived for section capacities and modulus in different stages of the composite sections. The predicted beam-column strength is compared with that of 331 beam-column tests with a wide range of parameters. A good agreement is obtained. The predicted load versus midspan deflection relationship for beam-columns is in good agreement with test results. A simplified model is developed for calculating the member capacity of concrete-filled SHS columns. Comparisons are made with predicted columns strengths using the existing codes such as LRFD (AISC 1994), AIJ (1997), and EC4 (1996). Simplified interaction curves are derived for concrete-filled beam-columns.

Thermal and flow characteristics of confined multiple slot jet impingement with exhaust ports (배기구를 가진 국한된 다중 슬롯 충돌제트의 열유동 특성)

  • Kang, Soo-Jin;Cho, Woo-Jin;Lee, Jong-Hyeok;Lee, Kwan-Soo
    • Proceedings of the SAREK Conference
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    • pp.835-840
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    • 2009
  • In this paper, confined multiple slot jet impingement with exhaust ports is investigated numerically. A flow cell, defined as volume sectioned by the impingement and confinement surfaces and the centerlines of adjacent nozzle and exhaust port, is chosen for computational domain. The effects of Reynolds number and geometrical parameters on the heat transfer performance and the flow characteristics are studied. For turbulence, the Abe-Kondoh-Nagano version of the low-Reynolds k-$\varepsilon$ model is employed. The results showed that the local Nusselt number distribution is shifted down and show poor heat transfer performance for small Reynolds number and small ratio of the lateral and axial length of flow cell. The rest of range, except the range of the shift phenomenon, can be classified into three groups by heat transfer characteristics.

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Eutectic Temperature Effect on Au Thin Film for the Formation of Si Nanostructures by Hot Wire Chemical Vapor Deposition

  • Ji, Hyung Yong;Parida, Bhaskar;Park, Seungil;Kim, MyeongJun;Peck, Jong Hyeon;Kim, Keunjoo
    • Current Photovoltaic Research
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    • v.1 no.1
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    • pp.63-68
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    • 2013
  • We investigated the effects of Au eutectic reaction on Si thin film growth by hot wire chemical vapor deposition. Small SiC and Si nano-particles fabricated through a wet etching process were coated and biased at 50 V on micro-textured Si p-n junction solar cells. Au thin film of 10 nm and a Si thin film of 100 nm were then deposited by an electron beam evaporator and hot wire chemical vapor deposition, respectively. The Si and SiC nano-particles and the Au thin film were structurally embedded in Si thin films. However, the Au thin film grew and eventually protruded from the Si thin film in the form of Au silicide nano-balls. This is attributed to the low eutectic bonding temperature ($363^{\circ}C$) of Au with Si, and the process was performed with a substrate that was pre-heated at a temperature of $450^{\circ}C$ during HWCVD. The nano-balls and structures showed various formations depending on the deposited metals and Si surface. Furthermore, the samples of Au nano-balls showed low reflectance due to surface plasmon and quantum confinement effects in a spectra range of short wavelength spectra range.

Seismic performance of the concrete-encased CFST column to RC beam joints: Analytical study

  • Ma, Dan-Yang;Han, Lin-Hai;Zhao, Xiao-Ling;Yang, Wei-Biao
    • Steel and Composite Structures
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    • v.36 no.5
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    • pp.533-551
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    • 2020
  • A finite element analysis (FEA) model is established to investigate the concrete-encased concrete-filled steel tubular (CFST) column to reinforced concrete (RC) beam joints under cyclic loading. The feasibility of the FEA model is verified by a set of test results, consisting of the failure modes, the exposed view of connections, the crack distributions and development, and the hysteretic relationships. The full-range analysis is conducted to investigate the stress and strain development process in the composite joint by using this FEA model. The internal force distributions of different components, as well as the deformation distributions, are analyzed under different failure modes. The proposed connections are investigated under dimensional and material parameters, and the proper constructional details of the connections are recommended. Parameters of the beam-column joints, including material strength, confinement factor, reinforcement ratio, diameter of steel tube to sectional width ratio, beam to column linear bending stiffness ratio and beam shear span ratio are evaluated. Furthermore, the key parameters affecting the failure modes and the corresponding parameters ranges are proposed in this paper.

A Study on the Design of Laterally Tilted SCH-SLD with Window Region (윈도우 영역을 갖는 측방향으로 경사진 SCH-SLD의 설계에 관한 연구)

  • 황상구;김정호;김운섭;김동욱;안세경;홍창희
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.4
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    • pp.777-790
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    • 2001
  • Theoretical analyses have been tried to design high power and stable operating SLD at 1.55${\mu}{\textrm}{m}$ wavelength range which is the lowest absorption wavelength in optical fiber. The materials of active layer and SCH layer were chosen as conventional In1-xGaxAsyPl-y quaternary composition systems. From the transverse mode and the lateral mode analyses of waveguide, the optical power distributions and the optical confinement factor have been studied for single-mode high power operation. According to these analyses, it was calculated the composition and the thickness of SCH layer to obtain the maximum optical confinement factor. In order to obtain low values of the reflectivity, we used the window region and the lateral tilted angle between tile active region and window region. And the reflectivity of SLD was calculated with the gaussian beam approximation and mode analysis. From these researches, it was confirmed for several results to fabricate the efficient and stable SLD. In case of using $1.3\mum$, InGaAsP SCH layer, the layer thickness was obtained $0.08\mum$, to get the maximum optical confinement factor. Using $0.2\mum$, active layer thickness and $0.08\mum$, SCH layer thickness, the window region length is about $100\mum$ without An coating, $10\mum$ in 1% AR coating to obtain about 10-4 reflectivity. When the tilted angle is about $10~15^{\circ}$, the reflectivity is about 10-3. From these results, if the window region length and tilted angle were controlled appropriately in given device structure, it was confirmed that it is possible to fabricate the stable SLD without AR coating analytically.

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Electrically Controllable Fiber Bragg Gratings with Liquid Crystal Cladding

  • Baek Seungin;Roh Sookyoung;Na Jun-Hee;Kwon Jaejoong;Yoon Ilyong;Chung Seunghwan;Jeong Cherlhyun;Lee Sin-Doo;Lee Byoungho;Jeong Yoonchan
    • Journal of the Optical Society of Korea
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    • v.9 no.3
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    • pp.123-128
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    • 2005
  • An electrically controllable fiber Bragg grating inscribed in a hydrogen-loaded standard single-mode fiber with liquid-crystal cladding is presented. Control of the optic axis of liquid crystals by means of external electric fields results in the change of reflectivity and Bragg wavelength of the grating. The increase of surrounding refractive index of a fiber makes effective refractive index of a propagation mode higher, which results in high field confinement and longer Bragg wavelength. The reduction of the fiber diameter by chemical etching process improves the long-range ordering of liquid-crystal molecules and reduces controlling voltage. The tunable ranges of reflectivity and Bragg wavelength of the liquid crystal-cladding fiber Bragg grating were $\~4.6dB\;and\;\~0.3nm$, respectively.

An Experimental Study on Stress-Strain Behavior of Confined Concrete Columns with Rectangular Sections (직사각형 단면 콘크리트 기둥의 응력-변형 거동에 관한 실험연구)

  • Oh, Byung-Hwan;Kim, Ki-Wan;Choi, Seung-Won;Park, Young-Ho
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.345-352
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    • 2005
  • The purpose of this study is to analyze the stress-strain behavior of confined concrete columns with rectangular section. Uniaxial concentric loading tests of nineteen concrete columns with rectangular section ($150{\times}100$, $250{\times}100$, $350{\times}100\;mm$) were conducted. The main variables are transverse reinforcement volumetric ratio and spacing, cross tie arrangement, cross-section aspect ratio, and concrete strength. From the present experiments, it was found that the increase of transverse reinforcement ratio increases the maximum stress and ductility ratio and the reduction of the spacing of transverse reinforcement also increases the ductility and effective confinement. The increase of the aspect ratio of the cross-section does not influence much the stress-strain behavior of rectangular columns within the aspect ratio range of 3.5. The effect of concrete strength on ductility is also discussed.

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Prediction of residual mechanical behavior of heat-exposed LWAC short column: a NLFE model

  • Obaidat, Yasmeen T.;Haddad, Rami H.
    • Structural Engineering and Mechanics
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    • v.57 no.2
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    • pp.265-280
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    • 2016
  • A NLFE model was proposed to investigate the mechanical behavior of short columns, cast using plain or fibrous lightweight aggregate concrete (LWAC), and subjected to elevated temperatures of up to $700^{\circ}C$. The model was validated, before its predictions were extended to study the effect of other variables, not studied experimentally. The three-dimensional NLFE model was developed using ANSYS software and involved rational simulation of thermal mechanical behavior of plain and fibrous LWAC as well as longitudinal and lateral steel reinforcement. The prediction from the NLFE model of columns' mechanical behavior, as represented by the stress-strain diagram and its characteristics, compared well with the experimental results. The predictions of the proposed models, considering wide range of lateral reinforcement ratios, confirmed the behaviors observed experimentally and stipulated the importance of steel confinement in preserving post-heating mechanical properties of plain and fibrous LWAC columns, being subjected to high temperature.

Hole Mobility Enhancement in (100)- and (110)-surface of Ultrathin-body(UTB) Silicon-on-insulator(SOI) Metal Oxide Semiconductors Field Effect Transistor (Ultrathin-body SOI MOSFETs에서 면방향에 따른 정공의 이동도 증가)

  • Kim, Kwan-Su;Cho, Won-Ju
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.11
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    • pp.939-942
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    • 2007
  • We investigated the characteristics of UTB-SOI pMOSFETs with SOI thickness($T_{SOI}$) ranging from 10 nm to 1 nm and evaluated the dependence of electrical characteristics on the silicon surface orientation. As a result, it is found that the subthreshold characteristics of (100)-surface UTB-SOI pMOSFETs were superior to (110)-surface. However, the hole mobility of (110)-surface were larger than that of (100)-surface. Especially, the enhancement of effective hole mobility at the effective field of 0.1 MV/cm was observed from 3-nm to 5-nm SOI thickness range.