• Title, Summary, Keyword: confinement

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Studying confined polymers using single-molecule DNA experiments

  • Hsieh, Chih-Chen;Doyle, Patrick S.
    • Korea-Australia Rheology Journal
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    • v.20 no.3
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    • pp.127-142
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    • 2008
  • The development of fluorescence microscopy of single-molecule DNA in the last decade has fostered a bold jump in the understanding of polymer physics. With the recent advance of nanotechnology, devices with well-defined dimensions that are smaller than typical DNA molecules can be readily manufactured. The combination of these techniques has provided an unprecedented opportunity for researchers to examine confined polymer behavior, a topic far less understood than its counterpart. Here, we review the progress reported in recent studies that investigate confined polymer dynamics by means of single-molecule DNA experiments.

The Lateral Confinment Effects of Spiral Reinforcement of High Strength Concrete Columns. (고강도 콘크리트 부재의 횡보강 효과에 관한 연구)

  • 신성우;권영호;이광수;오정근
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.63-67
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    • 1989
  • Various studies have been done to investigate the effectiveness of lateral confinement of lower strength concrete(below 420kg/$\textrm{cm}^2$). But little research its effectiveness for high strength concrete. A certain concern has been arised that the beneficial effect of lateral confinement in high strength concrete may be different from that in lower strength. This study aimed to investigate that concern with different confinement spacing(D/2 : D/4). The results show that beneficial effects of spiral confinement are more pronounced for lower strength concrete as compared to higher strength concrete.

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Confinement Steel based on Ductility Demand for RC Bridge Columns (철근콘크리트 교각의 연성요구량에 따른 심부구속철근량)

  • 손혁수;한상엽;조재원;이재훈
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.322-329
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    • 2002
  • The purpose of this study is to develop a reasonable design for transverse confinement reinforcement considering ductility and required transverse confinement reinforcement of RC bridge columns. In order to develop relationships between the curvature ductility and the displacement ductility, the analysis for total 21,600 columns using the computer program NARCC have been carried out for parametric studies. Based on the results from the parametric studies, a correlation equation between the curvature ductility and the displacement ductility was developed. In addition, an equation for calculating the required transverse confinement reinforcement based on ductility demand was developed for seismic design of RC bridge columns. The equations proposed by this study will provide more reasonable and more effective design guidelines for performance-based seismic design of RC bridge columns.

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Controlling Quantum Confinement and Magnetic Doping of Cesium Lead Halide Perovskite Nanocrystals

  • Dong, Yitong;Parobek, David;Son, Dong Hee
    • Journal of the Korean Ceramic Society
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    • v.55 no.6
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    • pp.515-526
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    • 2018
  • Cesium lead halide ($CsPbX_3$) nanocrystals have emerged as a new family of semiconductor nanomaterials that can outperform existing semiconductor nanocrystals owing to their superb optical and charge transport properties. Although these materials are expected to have many superior properties, control of the quantum confinement and isoelectronic magnetic doping, which can greatly enhance their optical, electronic, and magnetic properties, has faced significant challenges. These obstacles have hindered full utilization of the benefits that can be obtained by using $CsPbX_3$ nanocrystals exhibiting strong quantum confinement or coupling between exciton and magnetic dopants, which have been extensively explored in many other semiconductor quantum dots. Here, we review progress made during the past several years in tackling the issues of introducing controllable quantum confinement and doping of $Mn^{2+}$ ions as the prototypical magnetic dopant in colloidal $CsPbX_3$ nanocrystals.

Circumferential Confinement Effect of Circular Bridge Pier with FRP Wrapping in Earthquake (지진발생시 FRP 보강이 횡방향 구속에 미치는 효과)

  • 최영민;황윤국;권태규;윤순종
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.280-287
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    • 2003
  • The bridge columns with lap-splice reinforcements in earthquake suffered a brittle bond-slip failure due to the deterioration of lap-spliced longitudinal reinforcement without developing its flexural capacity or ductility. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP wrapping. The retrofitted columns using FRP laminated circular tube showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the circumferential confinement effect of existing circular bridge pier strengthened with FRP wrapping for poor lap-splice details. The effects on the confinement of FRP wrapping, such as gap lengths between footing and FRP, fiber orientations, and thicknesses of FRP, were investigated by Quasi-static experiments.

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Circumferential Confinement Effect on Lap-Spliced Reinforcements of Circular Bridge Pier (횡방향 구속이 교각의 겹침이음에 미치는 영향에 대한 고찰)

  • 최영민;황윤국;권태규;박경훈
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.339-342
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    • 2003
  • The bridge columns with lap-splice reinforcements in earthquake suffered a brittle bond-slip failure due to deterioration of the lap-spliced longitudinal reinforcements without developing its flexural capacity or ductility. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP wrapping. The retrofitted columns using FRP wrapping showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the circumferential confinement effect of existing circular bridge pier strengthened with FRP wrapping for poor lap-splice details. The effects on the confinement of FRP wrapping, such as gap lengths between footing and FRP, fiber orientations, and thicknesses of FRP, were investigated by quasi-static experiments.

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Compressive Strength Enhancement of Concrete Cylinders Confined with FRP Wrapping (FRP로 횡보강된 콘크리트 공시체의 압축강도 향상에 관한 연구)

  • 김영섭;정영수;박창규;송희원
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.351-354
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    • 2003
  • Triaxial behavior of concrete cylinders wrapped with FRP material has been investigated for the increase of concrete strength by lateral confinement. Using the model by Richart et al., a modified empirical equation was proposed to estimate the strength of concrete cylinders with FRP confinement based on the linear relationship between the concrete strength and lateral confining pressure. From the experimental stress-strain result of the cylinder specimens having similar confining pressure, less ductility was observed for higher strength concrete. But the compressive strength of the specimen was linearly increased by lateral confinement. The confinement effectiveness coefficient for the strength enhancement of the cylinders by FRP wrap was obtained as 2.27 from the regression analysis.

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Non-linear Analysis of Passive Confined Concrete Structures using Tri-Survace Concrete Model (Tri-Surface 콘크리트 모델을 이용한 수동 구속된 콘크리트의 비선형 해석)

  • 조병완;김장호;김영진
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.604-607
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    • 2003
  • Recently, hybrid concrete structures such as a concrete-filled steel tubular(CFT), a steel reinforced concrete(SRC) and a composite material are popular in structure applications. They also have merit of high strength, high ductility, and large energy absorption capacity. But the analysis of hybrid concrete structures is very difficult owing to the complex behavior of concrete under passive confinement. This paper has analyzed CFT, which receives passive confinement using Tri-Surface concrete model for three dimension finite element analysis. By the result of that, the proposed model was properly forecasted a concrete behavior that receives passive restraint as well as non-linear analysis of concrete which receive uniaxial stress and high active confinement of 400Mpa. If the model through the steady study is set up especially on the factor of concrete under passive confinement, the proposed concrete model will be surely useful for analysis of the hybrid concrete structures.

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Confinement Effects of High-Strength Reinforced Concrete Tied Columns

  • Han, Byum-Seok;Shin, Sung-Woo
    • International Journal of Concrete Structures and Materials
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    • v.18 no.2E
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    • pp.133-142
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    • 2006
  • An experimental study was conducted to investigate the effectiveness of transverse steel in reinforced concrete tied columns subjected to monotonically increasing axial compression. Eighteen large-scale columns($260{\times}260{\times}1,200mm$) were tested. Effects of such main variables as concrete compressive strength, configurations of transverse steel, transverse reinforcement ratio, spacing of transverse steel, and spalling of concrete cover were investigated. High-strength concrete columns under concentric axial loads show extremely brittle behavior unless the columns are confined with transverse steel that can provide sufficiently high lateral confinement pressure. A consistent decrease in the deformability of the column test specimens was observed with increasing concrete strength. Test results of this study were compared with existing confinement models of modified Kent-Park, Sheikh-Uzumeri, Mander, and Saatcioglu-Razvi. The comparison indicates many existing models to predict the behavior of confined concrete overestimate or underestimate the ductility of confined concrete.

An Experimental Study on the Structural Performance of Headed Bars by Lap Length and Confinement Details (겹침이음길이 및 구속 철근에 따른 헤드철근의 구조적 성능에 관한 실험적 연구)

  • Yu, Ho-Il;Lee, Yong-Taeg;Kim, Seung-Hun;Chea, Seo-Ho;Bahn, Byong-Youl
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.286-289
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    • 2006
  • Headed bars have used to the anchoring of the tension or compression longitudinal bars and of the shear reinforcing bars. Recently, lap splices of headed bars are attempted to the joints of precast concrete members and to the connections between old and new concrete members. Previous Michael's experimental research showed that confinement details had an effect on the lap splice performances of headed bars. In this study, the lap splice performances of headed bars(D25) with lap length and confinement details are evaluated through the experimental works. Four specimens, of which variables were the lap length of headed bar and the type of confine details, were tested for the performance evaluation on lap splice. Test results show that the lap length confinement reinforcement improve the performance of lap splice.

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