• Title/Summary/Keyword: 철근의 영향

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Effective Strengths of Concrete Struts in Strut-Tie Models of Reinforced Concrete Corbels (철근콘크리트 코벨 스트럿-타이 모델의 스트럿 유효강도)

  • Chae, Hyun Soo;Yun, Young Mook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.4
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    • pp.1081-1094
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    • 2014
  • The strut-tie model approach has proven to be effective in the ultimate analysis and design of structural concrete with disturbed regions. For the reliable analysis and safe design of the structural concrete, however, the effective strengths of concrete struts must be determined accurately. In this study, the equations of the effective strengths of concrete struts, which are useful for the three types of determinate and indeterminate strut-tie models of reinforced concrete corbels, were proposed. The effects of shear span-to-effective depth ratio, the vertical-to-horizontal force ratio, and flexural and horizontal shear reinforcement ratios were reflected in the development of the proposed equations. To examine the appropriateness of the proposed and existing equations, the ultimate strengths of 243 reinforced concrete corbels tested to failure were evaluated by using the three types of corbel strut-tie models.

An Experimental Study on Shear Behavior of Internal Reinforced Concrete Beam-Column Assembly (철근콘크리트 보-기둥 내부 접합부의 전단 거동에 관한 실험적 연구)

  • Lee, Jung-Yoon;Kim, Jin-Young;Oh, Ki-Jong
    • Journal of the Korea Concrete Institute
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    • v.19 no.4
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    • pp.441-448
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    • 2007
  • The beam-column assembly in a ductile reinforced concrete (RC) frames subjected to seismic loading are generally controlled by shear and bond mechanisms, both of which exhibit poor hysteretic properties. Hence the response of joints is restricted essentially to the elastic domain. The usual earthquake resistant design philosophy of ductile frame buildings allows the beams to form plastic hinges adjacent to beam-column assembly. Increased strain in these plastic hinge regions affect on joint strain to be increased. Thus bond and shear joint strength are decreased. The research reported in this paper presents the test results of five RC beam-column assembly after developing plastic hinges in beams. Main parameter of the test Joints was the amount of the longitudinal tensile reinforcement of the beams. Test results indicted that the ductile capacity of joints increased as the longitudinal tensile reinforcement of the beams decreased. In addition, both the tensile strain of the longitudinal reinforcement bars in the joint and the ductile ratio of the beam-column assemblages increased due to the yielding of steel bars in the plastic hinge regions.

Evaluation of the Effect of Coupler on the Ductility of Rebar by Uniaxial Tensile Test (1축 인장시험을 통한 커플러가 철근 연성도에 미치는 영향 평가)

  • Woo, Tae-Ryeon;Lee, Jong-Han;Cheung, Jin-Hwan;Jung, Chi-Young
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.1
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    • pp.90-98
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    • 2018
  • Recently, various reinforced concrete joints have been used in reinforced concrete structures. Therefore, it is important to grasp the tensile properties of the spliced rebar. In this study, uniaxial tensile tests were conducted on Grade 60 D22(#7), D29(#9), and two kinds of couplers manufactured according to ASTM A615 standard for evaluating ductility of coupler joints. The strain was measured using an image processing method more accurate and capable of measuring at various points freely. As the result of uniaxial tensile test, it was possible to calculate the stress-strain relationship and the longitudinal strain distribution according to the stress stages and it was founded that the average strain becomes lower as more occupying the coupler joint portions in the same gauge length. In addition, the empirical equations are proposed to account for the effect of the length of the coupler on the ultimate strain and the rupture strain.

Nonlinear Dynamic Analysis of RC Frames Based on Constitutive Models of Constituent Materials (재료의 구성모델에 따른 철근콘크리트 골조의 비선형 동적거동 특성 차이에 관한 연구)

  • Heo, YeongAe;Kang, Thomas H.K.
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.4
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    • pp.1-8
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    • 2013
  • Constitutive modeling of constituent materials is very important for reinforced concrete (RC) frames. Cyclic constitutive behavior of unconfined concrete, confined concrete and reinforcing steel should be well defined in fiber-based discretization of RC sections. This study performs nonlinear dynamic analyses of RC frame structures to investigate the sensitivity of seismic behavior of such frames to different constitutive models of constituent materials. The study specifically attempts to examine confinement effects in concrete modeling and degrading effects in steel modeling, which substantially affects the monotonic, cyclic and seismic responses of RC members and frames. Based on the system level analysis, it is shown that the response of non-ductile frames is less sensitive to confined concrete models while the modeling of reinforcing steel is quite influential to the inelastic response of both non-ductile and ductile frames.

Seismic-performance Flexural Experiments for Real Scale Piers with Circular Cross-section Considering Aging Effects (노후도를 고려한 실크기 원형단면 교각의 내진성능 휨실험)

  • Lee, Seung-Geon;Lee, Soo-Hyung;Lee, Hyerin;Hong, Kee-Jeung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.131-142
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    • 2021
  • For old piers constructed when seismic design code had not been developed, lap splices usually exist in plastic hinge region. Corrosion of rebars causes decreasement in cross-sectional area of rebar and deterioration of lap-splice behaviour, thereby reducing the seismic performance of the old piers. In this research, according to these characteristics of old piers, test specimens are designed and manufactured considering rebar corrosion, lap splice, seismic design details, and seismic reinforcement. These effects are investigated through experiments. As a result of these experiment, rebar corrosion as well as lap splice reduces displacement ductility. When seismic design details or steel-plate reinforcement are applied, sufficient displacement ductility is expressed. For non-seismically designed specimens, loosening of the lap splice of transverse rebars caused buckling of longitudinal rebars and crushing of core concrete in plastic hinge region . For seismically designed specimen, area-reducing and untying of transverse rebars due to corrosion of rebars caused buckling of longitudinal rebars and crushing of core concrete.

Current Status and Appropriate Check Method of Construction Quality Control for Rebar Coupler Splice (철근 커플러이음의 시공품질 확인 현황 및 적정 시공품질 확인 방안)

  • Kim, Ju-Yong;Kim, Jin-Dong;Lee, Young-Do;Kim, Gwang-Hee
    • Journal of the Korea Institute of Building Construction
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    • v.22 no.6
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    • pp.531-542
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    • 2022
  • As buildings become taller, the strength of structural materials must increase and the amount of rebar reinforcement also increases while the application of an appropriate rebar splice method in the construction process become one of the essential factors. In this research, the current status of quality check for rebar coupler is identified by an expert questionnaire and an appropriate quality check method is proposed through a quality test on specimens similar to actual on-site construction. In the test results, it was revealed that, among the quality check methods for rebar coupler joints, the coupler tightening method and face to face degree of between upper and lower rebar did not affect the strength the specimen. Therefore, it is considered to be an appropriate way to check the coupler quality check to check whether the threads are completely assembled during on-site construction through manufacture the number of threads of rebar and coupler with a margin beyond the calculated thread number.

Flexual-Shear Cracking Mechanism in Slender Reinforced Concrete Bems (철근콘크리트보의 휨전단균열 발생 메카니즘에 대한 연구)

  • Kim, Woo
    • Magazine of the Korea Concrete Institute
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    • v.10 no.3
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    • pp.185-196
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    • 1998
  • 이 논문은 직사각형 단면을 갖는 철근콘크리트 보에서 휨전단균열(Flexural-Shear Crack)이 원인을 규명하기 위해 모두 16개의 보를 실험한 결과를 기술한 것이다. 실험에 이용된 콘크리트보는 전단균열에 영향을 준다고 생각되는 몇 가지 요소를 인위적으로 소거 도는 고립되도록 특수하게 제작된 것이다. 이러한 특수보의 실험결과를 같은 재원을 갖는 보통의 정상보의 결과와 직접 비교하여서 그 차이를 분석함으로써 휨전단 균열의 발생원인을 규명하였다. 그 결과, 일반적인 콘크리트보에서의 휨전단균열 발생은 철근과 콘크리트의 경계면의 부착현상과 매우 밀접한 관련이 있는 것으로 나타났다. 또한 발생된 휨전단균열의 안정성은 주철근을 따라 발생되는 수평균열의 크기에 직접적인 영향을 받고 있는 것으로 나타났다. 본 연구에서 나타난 몇 가지 사실은 현재 사용중인 전단설계규준의 근본을 이루는 전단 위험단면개념과는 상반되는 것도 있었다. 실험에서 알아낸 사실을 근거로 전단파괴기구에 대한 새로운 가설을 제안하였다. 이 새 가설은 지금까지 잘 설명되지 않은 휨전단균열의 발생과 진행에 대한 원인 및 과정을 상당히 잘 설명해주고 있다고 생각된다.

Failure Modes of RC Beams with High Strength Reinforcement (고강도 비틀림보강철근을 사용한 철근콘크리트 보의 파괴모드)

  • Yoon, Seok-Kwang;Lee, Su-Chan;Lee, Do-Hyeong;Lee, Jung-Yoon
    • Journal of the Korea Concrete Institute
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    • v.26 no.2
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    • pp.143-150
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    • 2014
  • To avoid abrupt torsional failure due to concrete crushing before yielding of torsional reinforcement and control the diagonal crack width, design codes specify the limitations on the yield strength of torsional reinforcement of RC members. In 2012, Korean Concrete Institute design code increased the allowable maximum yield strength of torsional reinforcement from 400 MPa to 500 MPa based on the analytical and experimental research results. Although there are many studies regarding the shear behavior of RC members with high strength stirrups, limited studies of the RC members regarding the yield strength of torsional reinforcement are available. In this study, twelve RC beams having different yield strength of torsional reinforcement and compressive strength of concrete were tested. The experimental test results indicated that the torsional failure modes of RC beams were influenced by the yield strength of torsional reinforcement and the compressive strength of concrete. The test beams with normal strength torsional reinforcement showed torsional tension failure, while the test beams with high strength torsional reinforcement greater than 480 MPa showed torsional compression failure. Therefore, additional analytical and experimental works on the RC members subjected to torsion, especially the beams with high strength torsional reinforcement, are needed to find an allowable maximum yield strength of torsional reinforcement.

Confinement Range of Transverse Reinforcements for T-shaped Reinforced Concrete Walls (철근콘크리트 T형 벽체의 콘크리트 구속을 위한 횡철근의 배근범위)

  • 하상수;오영훈;최창식;이리형
    • Journal of the Korea Concrete Institute
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    • v.14 no.6
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    • pp.1001-1009
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    • 2002
  • The objective of this study is to determine the range of confinement (or the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The range of confinement for transverse reinforcement is related to the location of neutral axis and determined by the magnitude and distribution of compressive strain. The compressive strain depends on the ratio of wall cross sectional area to the floor-plan area, the aspect ratio, configuration, the axial load, and the reinforcement ratios. By affection of flange, the neutral axis appears different depending on positive and negative forces and because of this reason, when web and flange are subjected to compressive stress, the range of confinement for the transverse reinforcement of T-shaped walls would shows different result. Therefore this experimental research focused on the structural characteristics of T-shaped walls and suggested the neutral axis depth through comparing the results of this study with sectional analysis.

Evaluations of the Maximum Shear Reinforcement of Reinforced Concrete Beams (철근콘크리트 보의 최대 전단철근비에 대한 평가)

  • Hwang, Hyun-Bok;Moon, Cho-Hwa;Lee, Jung-Yoon
    • Journal of the Korea Concrete Institute
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    • v.21 no.6
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    • pp.719-727
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    • 2009
  • The requirements of the maximum shear reinforcement in the EC2-02 and CSA-04, which are developed based on the truss model, are quite different to those in the ACI-08 code and AIJ-99 code, which are empirical equations. The ACI 318-08, CSA-04, and EC2-02 codes provide an expression for the maximum amount of shear reinforcement ratio as a function of the concrete compressive strength, but Japanese code does not take the influence of the concrete compressive strength into account. For high strength concrete, the maximum amount of shear reinforcement calculated by the EC2-02 and CSA-04 is much greater than that calculated by the ACI 318-08. Ten RC beams having various shear reinforcement ratios were tested and their corresponding shear stress-shear strain curves and failure modes were compared to the predicted ones obtained by the current design codes.