• Title/Summary/Keyword: 원형철근

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Evaluation of the Shear Strength Component by Circular Transverse Reinforcement in Reinforced Concrete Columns (철근콘크리트 기둥에서 원형전단철근에 의한 전단강도 산정)

  • 하태훈;홍성걸
    • Journal of the Korea Concrete Institute
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    • v.14 no.6
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    • pp.982-988
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    • 2002
  • Current design equations for shear strength of reinforced concrete columns generally overestimate the shear strength contribution by the circular transverse reinforcement. This is due to the simplification of the discrete distribution of the reinforcement to the continuous one and the imprudent application of the classical truss model to the circular section, which is different in shear-resisting mechanism from the rectangular section. This study presents a rational model for the prediction of shear strength contribution by the circular transverse reinforcement considering the starting location of a diagonal crack, the number of transverse reinforcing bars crossing the main crack and the geometrical strength component of the transverse resistance. It was found that, for lower amount transverse reinforcement, the crack starting point and the number of crack crossing bars greatly influence the shear-resisting capacity. Proposed model leads to a reliable design equation which is derived using a linear regression method and is in good agreement with the lower bound of exact strength curve.

Evaluation of Effective Section Area of Shear Steel in Reinforced Concrete Circular Columns (철근콘크리트 원형기둥의 전단철근 유효단면적 평가)

  • 김장훈
    • Journal of the Korea Concrete Institute
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    • v.11 no.3
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    • pp.81-88
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    • 1999
  • In order to properly evaluate the shear strength of reinforced concrete circular columns due to the transverse shear reinforcement, the average of fractions of forces generated along the circular transverse hoops across the shear failure plane in the loading direction is calculated. For this, the center-to-center diameter of circular transverse hoops. spacing and the crack angle measured to the column longitudinal axis are considered. Using these variables, an equation representing the effective section area of circular transverse shear steel is proposed. The study result shows that the constant parameter. used for the calculation of the effective section area of circular hoops over the last 10 years, should not universally be applied any more. The use of the constant parameter may not seriously do harm to the evaluation of shear strength for circular columns with non-seismically designed transverse hoop reinforcement, since it gives slightly conservative results. However. for well-confined circular columns with close spacing or circular steel jacketing. it gives about 20% overestimation of the shear capacity contributed by the transverse hoop steel.

Study on the Characteristics of Uplift Capacity of Anchor Pin for Fixing the Vegetation Mat (식생매트 고정용 앵커핀의 인발력 특성에 관한 연구)

  • Kim, Hyun-Woo;Kim, Yun-Hwan;Kim, Chul
    • Proceedings of the Korea Water Resources Association Conference
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    • 2011.05a
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    • pp.319-324
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    • 2011
  • 최근 자연환경보전이라는 새로운 패러다임의 대두로 하천의 생태기능 향상을 위한 호안조성공법 중 하나인 식생매트호안 공법의 적용이 증가하고 있다. 국내 하천의 경우 비교적 큰 하상계수와 소류력의 증가로 식생매트 고정용 앵커핀의 기능 저하에 따른 호안의 피해가 발생하고 있다. 그러나 앵커핀의 외력저항성 연구 및 설치를 위한 기준이 마련되어 있지 않는 실정이다. 본 연구에서는 앵커핀의 인발특성을 연구함으로서 외력저항 특성을 파악하고자 하였다. 연구방법으로는 앵커핀을 관입시킨 토사에 인발장치를 연결하여 최대인발력과 인발력의 변화추이를 관찰하였다. 실험에 사용된 토사는 물다짐으로 다졌으며, 앵커핀은 식생매트 고정용으로 적용이 많은 이형철근형 앵커핀을 사용하였다. 대조군으로 형태가 동일한 원형철근을 이용하여 앵커핀을 제작 실험에 사용하였다. 실험조건은 앵커핀의 직경(10mm, 16mm)에 따른 주면과 침수토사의 배수시간 (48hr, 96hr, 144hr) 조절을 통한 함수율의 변화에 따른 인발특성을 관측하였다. 실험결과 평균 최대인발력의 변화는 48시간 배수시 직경변화에 따라 이형철근은 12.8N, 28N, 원형철근은 10.6N, 21N으로 나타났으며, 96시간 배수시 이형철근은 18.8N, 33N, 원형철근은 12.2N, 21.6N으로 나타났고, 144시간 배수시 이형철근은 21.4N, 36.4N, 원형철근은 20.4N, 33.2N으로 나타났다. 앵커핀의 인발력은 주면의 크기에 비례하며, 표면의 형태와 함수량에 따라 영향을 받는 것으로 나타났다. 따라서 이러한 앵커핀의 인발 특성을 파악하고, 식생호안에 적용한다면 피해를 최소화 할 수 있을 것으로 사료된다.

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Seismic Performance Assessment of Circular Reinforced Concrete Bridge Piers with Confinement Steel: II. Performance Assessment (원형 철근콘크리트 교각의 횡방향 철근에 따른 내진성능평가 : II. 성능평가)

  • Kim, Tae-Hoon;Kim, Young-Jin;Kang, Hyeong-Taek;Shin, Hyun-Mock
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.2A
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    • pp.351-361
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    • 2006
  • In this study, nonlinear finite element analysis procedures are presented for the seismic performance assessment of circular reinforced concrete bridge piers with confinement steel. This paper defines a damage index based on the predicted hysteretic behavior of a circular reinforced concrete bridge pier. Damage indices aim to provide a means of quantifying numerically the damage in circular reinforced concrete bridge piers sustained under earthquake loading. The proposed numerical method is applied to circular reinforced concrete bridge piers with confinement steel tested by the authors. The proposed numerical method gives a realistic prediction of seismic performance throughout the loading cycles for several test specimens investigated.

Seismic Performance Assessment of Reinforced Concrete Bridge Columns with Interlocking Circular Hoops (결합원형띠철근을 갖는 철근콘크리트 교각의 내진성능평가)

  • Kim, Tae-Hoon;Park, Kwang-Soon;Kang, Hyeong-Taek
    • Journal of the Earthquake Engineering Society of Korea
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    • v.15 no.6
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    • pp.81-90
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    • 2011
  • The purpose of this study was to investigate the seismic performance of reinforced concrete bridge columns with interlocking circular hoops. Three interlocking columns were tested under a constant axial load and a quasistatic, cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used for the analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated. Based on the experimental and analytical results, design recommendations are presented to improve the existing practice in the design and construction of reinforced concrete bridge columns with interlocking circular hoops.

Seismic Performance Assessment of Hollow Circular Reinforced Concrete Bridge Columns with Confinement Steel (중공원형 철근콘크리트 교각의 횡방향철근에 따른 내진성능평가)

  • Kim, Tae-Hoon;Kang, Hyeong-Taek
    • Journal of the Earthquake Engineering Society of Korea
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    • v.16 no.1
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    • pp.13-25
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    • 2012
  • The purpose of this study was to investigate the seismic behavior of hollow circular reinforced concrete bridge columns with confinement steel, and to develop improved seismic design criteria. Three hollow circular columns were tested under a constant axial load and a quasi-static, cyclically reversed horizontal load. The accuracy and objectivity of the assessment process can be enhanced by using a sophisticated nonlinear finite element analysis program. The numerical method used gives a realistic prediction of the seismic performance throughout the loading cycles for the several test specimens investigated. Based on the experimental and analytical results, design recommendations are presented to improve current practice in the design and construction of hollow circular reinforced concrete bridge columns.

Seismic Performance Assessment of Circular Reinforced Concrete Bridge Piers with Confinement Steel: I. Experiments and Analyses (원형 철근콘크리트 교각의 횡방향 철근에 따른 내진성능평가 : I. 실험 및 해석)

  • Kim, Tae-Hoon;Park, Se-Jin;Kim, Young-Jin;Kang, Hyeong-Taek
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.2A
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    • pp.339-349
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    • 2006
  • The purpose of this study is to investigate the seismic behavior of circular reinforced concrete bridge piers with confinement steel and to provide the data for developing improved seismic design criteria. Fourteen circular reinforced concrete bridge piers were tested under a constant axial load and a cyclically reversed horizontal load. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. In the companion paper, the proposed numerical method for the seismic performance assessment of circular reinforced concrete bridge piers with confinement steel is verified by comparison with experimental results.

Evaluation of Minimum Spiral Reinforcement Ratio of Circular RC Columns (철근콘크리트 원형기둥의 나선철근 최소철근비에 대한 평가)

  • Kim, Young-Seek;Kim, Hyeong-Gook;Park, Cheon-Beom;Kim, Sang-Woo;Kim, Kil-Hee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.6
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    • pp.1-9
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    • 2017
  • Spiral reinforcement in a circular column plays an effective role in the ductile behavior of a column through position fixing and buckling restraining of the longitudinal reinforcement, and confining core-concrete. Each country has suggested the minimum volumetric ratio of spiral reinforcement in order to secure the ductility of concrete columns. The minimum volumetric ratio of spiral reinforcement suggested by ACI 318-14 and the national concrete structure design standard was developed based on the theory of Richard et al. (1928); furthermore it has been used until now. However, their theory cannot consider the effects of high strength concrete and high strength reinforcement, and arrangement condition of the spiral reinforcement. In this study, a modified minimum volumetric ratio equation is suggested, which is required to improve the ductility of reinforced concrete circular columns and to recover their stress. The modified minimum volumetric ratio equation suggested here considers the effect of the compressive strength of concrete, the yield strength of spiral reinforcement, the cross sectional area of columns, the pitch of spiral reinforcements and the diameter of spiral reinforcement. In this paper, the validity of the minimum volumetric ratios from ACI 318-14 and this study was investigated and compared based on the results of uniaxial compression experiment for specimens in which the material strength and the spiral reinforcements ratio were used as variables. In the end of the study, the modification method for the suggested equation was examined.

Strength Degradation and Failure of Circular RC Bridge Columns with Longitudinal Steel Connection under Cyclic Lateral Load (반복횡하중을 받는 철근콘크리트 원형 교각의 축방향철근 연결상세에 따른 강도저감 및 파괴거동)

  • Lee Jae-Hoon;Jung Chul-Ho;Ko Seong-Hyun;Son Hyeok-Soo
    • Journal of the Korea Concrete Institute
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    • v.16 no.1 s.79
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    • pp.111-124
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    • 2004
  • This research is a part of a research program to verify the seismic performance of circular reinforced concrete bridge columns with respect to longitudinal steel connection details under cyclic lateral load. A total of 21 column specimens were constructed and tested. Main variables in this test program were longitudinal steel connection details(continuous, lap-spliced, and mechanically connected), confinement steel ratio, and axial force ratio, etc. The test results of the columns with different longitudinal steel connection details showed different failure mode, strength degradation, and seismic performance. From the quasi-static test, it was found that the columns with all longitudinal reinforcement lap-spliced showed significantly reduced ductility. However, seismic performance of the columns with half of longitudinal reinforcement lap-spliced showed limited ductility but much more ductile behaviour than the columns with all longitudinal reinforcement lap-spliced. It was also found that the seismic performance, failure mode and strength degradation of columns with mechanical connected longitudinal reinforcement were similar to those of columns with continuous longitudinal reinforcement.

Seismic Performance of Circular RC Bridge Columns with Longitudinal Steel Connection Details (축방향철근 연결상세에 따른 철근콘크리트 원형교각의 내진성능)

  • Lee Jae-Hoon;Son Hyeok-Soo;Ko Seong-Hyun
    • Journal of the Korea Concrete Institute
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    • v.16 no.2 s.80
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    • pp.249-260
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    • 2004
  • The longitudinal steel connection of reinforced concrete bridge column is sometimes practically unavoidable, however the current Korean bridge design specifications have no special provisions about lap-splices of longitudinal steel. This paper reports experimental results of a research program investigating the seismic performance of circular RC bridge columns with respect to longitudinal steel connection detailing. Twenty-one circular column specimens were tested under quasi-static test. The columns with the entire longitudinal steel lap-spliced within plastic hinge region show relatively sudden strength degradation and low ductility than the columns with continuous longitudinal steel and the columns with half of longitudinal steel lap-spliced. However, the seismic performance of the column with mechanically connected longitudinal steel is similar to that of the column with continuous longitudinal steel. The final objectives of this study are to suggest appropriate longitudinal reinforcement connection details for the limited ductility design concept and to provide quantitative reference data and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, collapse, etc. Ultimate displacement/drift ratio, displacement ductility, response modification factor, equivalent viscous damping ratio, residual deformation index, and effective stiffness are investigated and discussed in this paper.