• Title/Summary/Keyword: effective rectangular stress block.

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A Study on Axial Force - Moment Capacity of High-Strength Concrete Tied Column Sections (고강도 콘크리트 기둥단면의 축력-모멘트 강도에 관한 연구)

  • 박해균;박동규;박영식;손영현;이재훈
    • Proceedings of the Korea Concrete Institute Conference
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    • 1996.04a
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    • pp.300-305
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    • 1996
  • Reinforced concrete column is an effective structural element to take advantage of high strength concrete. This paper presents an experimental and analytical strength of high strength concrete rectangular tied column sections under eccentric loading. The test variables are concrete strength, steel ratios, slenderness and eccentricity. The analytical results of the ACI's rectangular stress block, Zia's modified rectangular stress block, and a trapezoid block are compared with experimentally obtained data. It may be concluded that the trapezoid stress block provided the most reasonable column section capacities for high strength concrete columns.

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An Experimental and Analytical Study on Axial Force-Moment Capacity of High-Strength Concrete Column under Eccentric Loads (편심을 받은 고강도 콘크리트 기둥의 출력-모멘트 강도에 관한 실험 및 해석적 연구)

  • 최창익;손혁수;이재훈
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.04a
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    • pp.468-474
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    • 1997
  • High strength concrete is a more effective material for columns subject to axial force and moment than for other structural elements. The purpose of this study is to review strength calculation methods for high strength concrete columus by comparison of analytical values and experimental results. The variables of column test under eccentric loading were concrete compressive strength, longitudinal steel ratio, and eccentricity of load. The tied column sections of 120×120mm and 210×210mm were tested and the eccentricity of load varied in the range from 0.16 times to 0.54 times the column depth. The analytical results using the stress-strain relationship to 0.54 times the column depth. The analytical results using the stress-strain relationship as well as the ACI's rectangular block, Zia's modified block, and the trapezoidal block are compared with experimentally obtained data, and discussed in this paper.

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Stress Block of High Strength Polymer Concrete Flexural Members (고강도 폴리머 콘크리트 휨부재의 응력블럭)

  • 김관호;김남길;연규석
    • Journal of the Korea Concrete Institute
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    • v.14 no.5
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    • pp.638-644
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    • 2002
  • The stress-strain relationship of polymer concrete flexural member was evaluated using C-shaped polyester concrete specimen, the compressive strength of which is 1400 kgf/$\textrm{cm}^2$. Eccentric compression test was performed to estimate the parameters, ${\alpha}$, ${\beta}$1, ${\gamma}$ for equivalent rectangular stress block. The ultimate moment strength ware obtained from the bending test on reinforced polymer concrete beams which were prepared with S different tensile steel ratios with a shear span ratio of 4.0. These values were compared with theoretical ultimate moment strengths, which were obtained using the parameters ${\alpha}$=0.61 and ${\beta}$1=0.73 from stress-stain curves of C-shaped specimens. The results showed that, when tensile steel ratio was over 0.50 $\rho$b, the experimentally obtained moment strengths were well matched with theoretically calculated values. In order to develop accurate criteria for polymer concrete flexural members, however, many other expermental studies for parameter determination are necessary using C-shaped specimens which have various compressive strengths and different sizes.

Effect of confinement on flexural ductility design of concrete beams

  • Chen, X.C.;Bai, Z.Z.;Au, F.T.K.
    • Computers and Concrete
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    • v.20 no.2
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    • pp.129-143
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    • 2017
  • Seismic design of reinforced concrete (RC) structures requires a certain minimum level of flexural ductility. For example, Eurocode EN1998-1 directly specifies a minimum flexural ductility for RC beams, while Chinese code GB50011 limits the equivalent rectangular stress block depth ratio at peak resisting moment to achieve a certain nominal minimum flexural ductility indirectly. Although confinement is effective in improving the ductility of RC beams, most design codes do not provide any guidelines due to the lack of a suitable theory. In this study, the confinement for desirable flexural ductility performance of both normal- and high-strength concrete beams is evaluated based on a rigorous full-range moment-curvature analysis. An effective strategy is proposed for flexural ductility design of RC beams taking into account confinement. The key parameters considered include the maximum difference of tension and compression reinforcement ratios, and maximum neutral axis depth ratio at peak resisting moment. Empirical formulae and tables are then developed to provide guidelines accordingly.