• Title, Summary, Keyword: confinement

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Proposed Design Provisions for Development Length Considering Effects of Confinement

  • Choi, Oan-Chul;Kim, Byoung-Kook
    • International Journal of Concrete Structures and Materials
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    • v.18 no.1E
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    • pp.49-54
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    • 2006
  • Confinement is major contribution to bond strength between reinforcement steel bars and concrete. Cover thickness, bar spacing and transverse reinforcement are the key confinement factors of current provisions for the development and splices of reinforcement. However, current provisions are still too complicated to determine the values of the confinement, which need to be well delineated in the process of design. In this study, an experimental work using beam-end and splice specimens was performed to examine the effect of concrete cover on bond strength. The results of this experiment and previously available data are analyzed to identify the effects of confinement on bond strength. From this reevaluation, new provisions for the development and splices of reinforcement are proposed. The provisions suggest some limitations in the confinement index. The new provisions will allow the engineers to use a simple and yet satisfactory and appropriate method or a precise approach for design to determine the values of confinement on the calculation of development and splice lengths.

Redistribution of moments in reinforced high-strength concrete beams with and without confinement

  • Lou, Tiejiong;Lopes, Sergio M.R.;Lopes, Adelino V.
    • Structural Engineering and Mechanics
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    • v.55 no.2
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    • pp.379-398
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    • 2015
  • Confinement is known to have important influence on ductility of high-strength concrete (HSC) members and it may therefore be anticipated that this parameter would also affect notably the moment redistribution in these members. The correctness of this "common-sense knowledge" is examined in the present study. A numerical test is performed on two-span continuous reinforced HSC beams with and without confinement using an experimentally validated nonlinear model. The results show that the effect of confinement on moment redistribution is totally different from that on flexural ductility. The moment redistribution at ultimate limit state is found to be almost independent of the confinement, provided that both the negative and positive plastic hinges have formed at failure. The numerical findings are consistent with tests performed on prototype HSC beams. Several design codes are evaluated. It is demonstrated that the code equations by Eurocode 2 (EC2), British Standards Institution (BSI) and Canadian Standards Association (CSA) can well reflect the effect of confinement on moment redistribution in reinforced HSC beams but the American Concrete Institute (ACI) code cannot.

Role of Quantum Confinement Effect on Tunneling Operation of LTFET Devices

  • Najam, Faraz;Yu, Yun Seop
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.241-242
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    • 2017
  • Part of the channel in L-shaped tunnel field-effect transistor (LTFET) is very thin and suffers from quantum confinement effect. Role of quantum confinement effect on band-to-band-tunneling (BTBT) of LTFET was investigated using numerical simulation and band diagram analysis. It was found that quantum confinement effect significantly affects the BTBT mechanism of LTFET devices.

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Modeling of a Confinement Effect in Laser Shock Peening on Titanium Alloy (티타늄 합금에 대한 레이저 쇼크 피닝에서 컨파인먼트에 따른 피닝 효과 모델링)

  • Lee, Wooram;Kim, Joohan
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.22 no.4
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    • pp.680-685
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    • 2013
  • In this study, the effect of laser shock peening on a titanium alloy was modeled using different confinements. Both liquid and solid confinement could be applied to laser shock peening, and solid confinement provided a dry laser shock peening process, which has the advantage of a corrosion-free effect. When a different confinement was applied to laser shock peening, a different peening effect would be expected. In our study, the peening effect was numerically modeled and simulated. The main effect of different confinements was a change in the impedances required to confine a shock wave from a plasma. The impedances were assumed with respect to different materials. Johnson-Cook's plastic deformation modeling was applied to the simulation. The strains and residual stresses were calculated to evaluate the confinement effects. When solid confinement was used, the residual stress increased by 60-85%, compared to the case of liquid confinement. However, the depth of the residual stress was slightly deeper. The simulated results could be applied to estimate the peening effect when a different confinement was used in the laser shock peening process.

Confinement Effect of Reinforced Concrete Members Using a Parabola-Rectangular Compressive Stress-Strain Relationship (포물선-직선 압축응력-변형률 관계를 이용한 철근콘크리트 부재의 횡구속 효과)

  • Choi, Seung Won;Kim, Woo
    • Journal of the Korea Concrete Institute
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    • v.27 no.1
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    • pp.45-53
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    • 2015
  • In general, RC columns are reinforced by spiral or tied steel and a strength of confined concrete is more increased than this of unconfined concrete. And strength and ductility of column are increased by a confinement effect. A confinement effect is affected by concrete strength, spacing, volume and strength of confinement steel. Many researchers suggested various confinement models which reflected these parameters by many experimental results. In this study, a load-strain relationship is evaluated by a confinement model in EC2, and it is compared with Mander model, Saatchioglu-Razvi model and Cusson et al. model. As results, it is appeared that a confinement model in EC2 is able to apply all kinds of concrete strength and a consistency in sectional analysis can be secured using material models in EC2. In parameter studies using material models in EC2, a confinement effect is more affected by a confinement steel than a concrete strength.

Variations in Ductility of Shear Wall with Length of Boundary Confinement (단부 횡보강영역에 따른 전단벽 연성도의 변화)

  • 강수민;오재은;박홍근
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.853-858
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    • 2001
  • Experimental studies were peformed to investigate variations in ductility of shear wall with length of boundary confinement. Eight specimens containg different lengths of confinment zone, which model compressive zone in plastic regions of shear walls, were tested against eccentric vetical load. Stress-strain model for confined concrete was used to predict strength and ductility of the specimens, which was compared to the test results. The results obtained show that failure of the compressive zone occurs in a brittle manner when the stress of unconfined zone softened after the ultimate strength were reached. To enhance the ductility of shear walls with concentrated confinement zone such as barbell-type walls, the ultimate strength of the confinement zone needs to be increased, and for shear walls with distributed confinement zone the length of the confinement zone needs to be extended.

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Deformability and Confinement of Structural Wall with Boundary Element (단부횡보강된 구조벽의 변형능력 및 보강방법)

  • 강수민;박홍근
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.349-361
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    • 2003
  • For performance-base design using nonlinear static analysis, it is required to predict the inelastic behavior of structural members accurately. In the present study, nonlinear numerical analysis was performed to develop the method describing the moment-curvature relationship of structural wall with boundary confinement. Through the numerical analysis, variations of behavioral characteristics and failure mechanism with the arrangement of vertical reiforcement and the length of boundary confinement were studied. Based on the findings, moment-curvature curves and curvature capacity for walls with a variety of re-bar arrangement was developed. By equalizing curvature capacity to demand, a design method which can determine the length of boundary confinement, was developed and for the effectiveness of boundary confinement and constructability, boundary confinement detail was proposed.

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Effects of Carbon-Fiber Sheets on Lateral Confinement in Columns of RC Buildings in Rural Area (농어촌 지역 RC 건축물 기둥 부재의 탄소섬유시트 횡보강 효과)

  • Kim, Yoon IL;Chun, Hyung Min
    • Journal of the Korean Institute of Rural Architecture
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    • v.6 no.3
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    • pp.106-115
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    • 2004
  • In this paper, the compressive strength and ductility enhancement of concrete by lateral confinement of carbon-fiber sheets(CFS) have been studied experimentaly with cylinder specimens and square short columns reinforced externally by CFS. Test variables were amount of lateral reinforcement by CFS and space of hoop bars. Test results showed that lateral reinforcements by carbon-fiber sheets provided lateral confinement successfully for the concrete specimens and were more effective for ductility enhancement than for strength increase, and that the lateral confinement coefficient of cabon-fiber sheets increased according to narrowing the space of hoop bars in the double lateral confinement made by CFS and hoop bars.

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Effects of confinement reinforcement and concrete strength on nonlinear behaviour of RC buildings

  • Yon, Burak;Calayir, Yusuf
    • Computers and Concrete
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    • v.14 no.3
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    • pp.279-297
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    • 2014
  • This paper investigates the effects of confinement reinforcement and concrete strength on nonlinear behaviour of reinforced concrete buildings (RC). For numerical application, an eleven-storey and four bays reinforced concrete frame building is selected. Nonlinear incremental static (pushover) analyses of the building are performed according to various concrete strengths and whether appropriate confinement reinforcement, which defined in Turkish seismic code, exists or not at structural elements. In nonlinear analysis, distributed plastic hinge model is used. As a result of analyses, capacity curves of the frame building and moment-rotation curves at lower end sections of ground floor columns are determined. These results are compared with each other according to concrete strength and whether appropriate confinement reinforcement exists or not, respectively. According to results, it is seen that confinement reinforcement is important factor for increasing of building capacity and decreasing of rotations at structural elements.

Compressive behaviour of circular steel tube-confined concrete stub columns with active and passive confinement

  • Nematzadeh, Mahdi;Hajirasouliha, Iman;Haghinejad, Akbar;Naghipour, Morteza
    • Steel and Composite Structures
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    • v.24 no.3
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    • pp.323-337
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    • 2017
  • This paper presents the results of a comprehensive experimental investigation on the compressive behaviour of steel tube-confined concrete (STCC) stub columns with active and passive confinement. To create active confinement in STCC columns, an innovative technique is used in which steel tube is laterally pre-tensioned while the concrete core is simultaneously pre-compressed by applying pressure on fresh concrete. A total of 135 STCC specimens with active and passive confinement are tested under axial compression load and their compressive strength, ultimate strain capacity, axial and lateral stress-strain curves and failure mode are evaluated. The test variables include concrete compressive strength, outer diameter to wall thickness ratio of steel tube and prestressing level. It is shown that applying active confinement on STCC specimens can considerably improve their mechanical properties. However, applying higher prestressing levels and keeping the applied pressure for a long time do not considerably affect the mechanical properties of actively confined specimens. Based on the results of this study, new empirical equations are proposed to estimate the axial strength and ultimate strain capacity of STCC stub columns with active and passive confinement.