• Title, Summary, Keyword: 횡철근

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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.

Confined Effect of High-Strength Reinforcement Considering Reduction of Raw Materials (원자재 절감을 고려한 고강도 강재의 횡구속 효과)

  • Kim, Min-Jun;Kim, Do-Jin;Kim, Yeong-Sik;Kim, Sang-U;Baek, Seung-Cheol;Kim, Gil-Hui
    • Proceedings of the Korean Society for Emotion and Sensibility Conference
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    • pp.261-264
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    • 2009
  • 강재의 고강도화는 원자재 부족을 해결할 수 있는 방안으로 친환경적이며 인간의 문명을 지속가능하게 하는 방법으로 인식 되고 있다. 따라서 본 연구에서는 고강도 강재의 횡구속 능력을 평가하기 위해 나선철근을 사용한 횡구속실험을 수행하였다. 실험의 주변수는 단면형상, 철근비로 하고 콘크리트의 강도는 25MPa로 계획하였다. 실험 결과, 단면형상에 따라 원형 실험체가 각형 실험체보다 우수한 횡구속 효과를 나타내는 것을 확인하였다. 또한 횡보강근의 철근비가 증가할수록 횡구속 효과가 증가하는 경향을 나타내었다.

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A stress-strain Model of High-strength concrete confined with Transverse Reinforcement (횡보강철근으로 구속된 고강도 콘크리트의 응력-변형률 구속 모델)

  • Moon, Cho-Hwa;Park, Jong-Wook;Kim, Sang-Woo;Kim, Kil-Hee;Lee, Jung-Yoon
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.87-88
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    • 2010
  • The strength and ductile capacity of reinforced concrete column can be improved by confinement using transverse reinforcement. Variety stress-strain models about the reinforced concrete confined by transverse reinforcement has been proposed. In this paper, parameters which effect to the ultimate confinement stress of circular cylinder confined by high strength transverse steel is examined. And the possion's ratio equation is proposed by analysis of strain between concrete and transverse reinforcement.

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Effects of Transverse Reinforcement on Headed Bars with Large Diameter at Cut-off Points (컷오프 구간에 정착된 대구경 확대머리철근에 대한 횡보강근의 효과)

  • Jung, Hyung-Suk
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.5
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    • pp.82-90
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    • 2018
  • The nuclear structures are composed of large diameter bars over No.36. If the hooked bars are used for anchorage of large diameter bars, too long length of the tail extension of the hook plus bend create congestion and make an element difficult to construct. To address those problems, headed bars were developed. Provisions of ACI 318-08 specify the development length of headed bars and ignore the effect of transverse reinforcement based on the background researches. However, if headed bars are used at the cut-off or lap splice, longitudinal reinforcements, which are deformed in flexural members, induce tensile stress in cover concrete and increase the tensile force in the transverse reinforcement. The object of this research is to evaluate the effects of transverse reinforcement on the anchorage capacity of headed bar so anchorage test with variable of transverse rebar spacing was conducted. Specimens, which can consider the behavior at the cut-off, were tested. Test results show that failure of specimen without transverse reinforcement was sudden and brittle with concrete cover lifted and developed stress of headed bars was less than half of yield strength of headed bars. On the other hand, in the specimen with transverse reinforcement, transverse rebar directly resist the load of free-end so capacity of specimens highly increased.

Assessment of Ductility and Plastic Hinge Region of Reinforced Concrete Multi-Column Bent (2주형 다주교각의 연성도 및 소성힌지 영역에 관한 연구)

  • Byun, Soon-Joo;Im, Jung-Soon
    • Journal of Korean Society of Hazard Mitigation
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    • v.6 no.3
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    • pp.37-45
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    • 2006
  • In this study, displacement ductility capacity and plastic hinge regions of reinforced concrete multi-column bent with different transverse reinforcement ratio are investigated. The ductility increases remarkably as transverse reinforcement ratio increase and the multi-column bent loaded along transverse direction is more ductile. The plastic hinge length for special detailing requirements of transverse reinforcement is estimated. For high target ductility, plastic hinge length for confinement should be extended with increased transverse reinforcement ratio. The plastic hinge length of multi-column bent loaded along transverse direction is shorter than that along longitudinal direction, because of the different moment distribution.

Generalized Lateral Load-Displacement Relationship of Reinforced Concrete Shear Walls (철근콘크리트 전단벽의 횡하중-횡변위 관계의 일반화)

  • Mun, Ju-Hyun;Yang, Keun-Hyeok
    • Journal of the Korea Concrete Institute
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    • v.26 no.2
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    • pp.159-169
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    • 2014
  • This study generalizes the lateral load-displacement relationship of reinforced concrete shear walls from the section analysis for moment-curvature response to straightforwardly evaluate the flexural capacity and ductility of such members. Moment and curvature at different selected points including the first flexural crack, yielding of tensile reinforcing bar, maximum strength, 80% of the maximum strength at descending branch, and fracture of tensile reinforcing bar are calculated based on the strain compatibility and equilibrium of internal forces. The strain at extreme compressive fiber to determine the curvature at the descending branch is formulated as a function of reduction factor of maximum stress of concrete and volumetric index of lateral reinforcement using the stress-strain model of confined concrete proposed by Razvi and Saatcioglu. The moment prediction models are simply formulated as a function of tensile reinforcement index, vertical reinforcement index, and axial load index from an extensive parametric study. Lateral displacement is calculated by using the moment area method of idealized curvature distribution along the wall height. The generalized lateral load-displacement relationship is in good agreement with test result, even at the descending branch after ultimate strength of shear walls.

Failure Behavior of Octagonal Flared RC Columns Using Oblong Hoops (장방형 띠철근을 이용한 팔각형 플레어 RC 기둥의 파괴거동)

  • Ko, Seong-Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.3
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    • pp.58-68
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    • 2014
  • Transverse steel bars are used in the plastic hinge zone of columns to insure adequate confinement, prevention of longitudinal bar buckling and ductile behavior. Fabrication and placement of rectangular hoops and cross-ties in columns are difficult to construct and require larger amount of transverse steels. In this paper, to solve these problems, the new lateral confinement method using oblong hoop is proposed for the transverse confinement of columns of the oblong cross-section and flared column. The experimental study for octagonal oblong cross-section was carried out by the flared columns test in strong axis. The lateral confinement method using proposed oblong hoop detail showed satisfactory performance of lateral confinement. Therefore it can be the alternative for oblong cross-section and flared column with improved workability and cost-efficiency.

Experimental Study on Structural Performance of Recycled Coarse Aggregate Concrete Confined by Steel Spirals (나선철근으로 횡구속된 순환골재 콘크리트의 구조적 성능에 관한 실험적 연구)

  • Kim, Sang Woo;Jung, Chang Kyo;Lee, Sun Hee;Kim, Kil Hee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.1
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    • pp.103-111
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    • 2011
  • This paper estimated the structural behavior of recycled aggregate concrete confined with spiral reinforcement. The main test parameter was designed to be the type of aggregates and the steel ratio of spirals. A total of 18 specimens were cast and tested in this study. All the specimens had a diameter of 150mm and a height of 300mm. The specimens can be divided into two groups, based on the type of coarse aggregate used. The ratio of spiral reinforcement was varied from 0 % to 1.75%. To measure the axial and lateral deformations of the specimens, a total of six linear variation displacement transducers (LVDTs) were installed at each specimen. Furthermore strain gauges were also attached to the steel spirals to obtain the strain of spiral reinforcements. From the experimental results, the structural performance of recycled aggregate concrete specimens confined by steel spirals was similar to that of natural aggregate concrete specimens regardless of the ratio of spiral reinforcement.

Cyclic Behavior of High-Performance Fiber-Reinforced Cement Composite Coupling Beam Having Diagonal Reinforcement (대각철근을 갖는 고성능 섬유보강 시멘트 복합체 연결보의 이력거동 평가)

  • Kwon, Hyun-Wook;Jeon, Yong-Ryul;Lee, Ki-Hak;Shin, Myung-Su;Han, Sang-Whan
    • Journal of the Korea Concrete Institute
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    • v.25 no.6
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    • pp.649-656
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    • 2013
  • Coupled shear walls can provide an efficient structural system to resist lateral force. However, the reinforcement detail for diagonally reinforced coupling beams required by ACI-318 often causes the difficulties in construction due to the reinforcement congestion and interference among reinforcement. This paper is to evaluate cyclic behavior of High-Performance Fiber-Reinforced Cement Composite (HPFRCC) coupling beams having reduced transverse reinforcement around the beam perimeter. Experimental test was conducted using three specimens having a beam aspect ratio 2.0. Test results showed that HPFRCC coupling beams with half of transverse reinforcement required by ACI-318 provided similar energy dissipation capacities compared with the coupling beams having reinforcement satisfy the requirement of ACI-318.

Behavior and Capacity of Compression Lap Splice in Confined Concrete with Compressive Strength of 40 and 60 MPa (횡보강근이 있는 40, 60 MPa 콘크리트에서 철근 압축이음의 거동과 강도)

  • Chun, Sung-Chul;Lee, Sung-Ho;Oh, Bo-Hwan
    • Journal of the Korea Concrete Institute
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    • v.21 no.4
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    • pp.389-400
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    • 2009
  • A compression lap splice can be calculated longer than a tension lap splice in high strength concrete according to current design codes. Including effects of transverse reinforcement, a compression splice becomes much longer than a tension splice. Effects of transverse reinforcement and bar size on strength and behavior of compression lap splice, which always exist in actual structures, have been investigated through experimental study of column tests with concrete strength of 40 and 60 MPa. The results of the tests with bar diameters of 22 and 29 mm show that there is no size effect of bar diameter on compression lap splice. Bond strength of small bar diameter may increase. However, large diameters of re-bars are used in compression member and the size effect of re-bars does not have to be considered in compression lap splice. Confined specimens have twice of calculated strengths by current design codes. New design equations for the compression lap splice including the effects of transverse reinforcement are required for practical purpose of ultra-high strength concrete. End bearing is enhanced by transverse reinforcement placed at ends of splice not by transverse reinforcement within splice length. As more transverse reinforcement are placed, the stresses developed by bond linearly increase. The transverse reinforcements at ends of splice a little improve the strength by bond. Because the stresses developed by bond in compression splice with transverse reinforcement are nearly identical to or less than those in tension splice with same transverse reinforcement, strength increment of compression splice is attributed to end bearing only.