• Title/Summary/Keyword: Standard hooked bars

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Effects of Steel Fiber Reinforcement and the Number of Hooked Bars at R/C Exterior Joints

  • Choi, Ki-Bong
    • KCI Concrete Journal
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    • v.11 no.3
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    • pp.181-189
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    • 1999
  • An experimental study was performed on the Pull-out behavior of 90-deg standard hooks from the exterior beam-column connections. the effects of the number of hooked bars and fiber reinforcement of the joint area were investigated with the following conclusions : (1) Under the pull-out action of hooked bars. the damage and cracking of joint area the number of hooks pulling out from a joint increases; (2) Substitution of the transverse column (confining) reinforcement with steel fibers at the joint region effectively reduces the extent of cracking in exterior joints caused by the pull-out of hooked bars; (3) The pull-out strength and post-peak ductility of hooked bars are adversely influenced by the increase in number of hooks pulling out from an exterior joint. Current hooked bar anchorage design guidelines may be improved by considering the effect of the number of hooked bars on anchorage conditions at the exterior joints; and (4) The strength and ductility of hooked bars under pull-out forces are positively influenced by substituting the conventional confining reinforcement of exterior joints with steel fibers . The application of steel fibers to the exterior joints is an effective technique for improving the anchorage conditions of hooked bars, and also for reducing the congestion of reinforcement in the beam-column connections.

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Effects of the Number of Hooked Bars on Anchorage Conditions at Exterior Joints (외측 보-기둥 접합부의 정착 상태에 관한 훅크철근의 영향)

  • Choi, Ki-Bong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.1 no.2
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    • pp.151-156
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    • 1997
  • An experimental study was performed on the pull-out behavior of 90-deg standard hooks from exterior beam-column connections. The effects of the number of hooked bars of joint area were investigated. Under the pull-out action of hooked bars, the damage and cracking of joint area tends to be more extensive as the number of hooks pulling out from a joint increases. The pull-out strength and post-peak ductility of hooked bar are adversely influenced by the increase in number of hooks pulling out from an exterior joint. Current hooked bar anchorage design guidelines may be improved by considering the effect of the number of hooked bars on anchorage conditions at exterior joints.

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Development Length of High-Strength Standard Hooked Bars (550MPa) in Nuclear Power Plant Structures (고강도철근(550MPa)의 원전구조물 적용을 위한 표준갈고리 정착설계)

  • Lee, Byung Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2018.05a
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    • pp.99-100
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    • 2018
  • Because of the congestion problems, the high-strength reinforcements are expected to be used in nuclear power plant structures in the near future. According to ACI 349-13, it is permitted to use the high-strength(550MPa) hooked bars in design of development length, but there is no special equation for high-strength bars. In order to reflect the anchorage capacity and behavior properties of high-strength bars with large-diameter(43 & 57mm), it is necessary to develope the new development length equation for large-size and high-strength bars.

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ACI 349 Code Change to Use the Gr.80 Headed Deformed Bars in Nuclear Power Plant Structures (Gr.80 확대머리철근의 원전구조물 적용을 위한 ACI 349 코드개정에 관한 연구)

  • Lee, Byung Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2017.05a
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    • pp.200-201
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    • 2017
  • Generally, a lot of reinforcements are used in nuclear power plant concrete structures, and it may cause several potential problems when concrete is poured. Because of the congestion caused by hooked bars, embedded materials, and other reinforcements, it is too difficult to pour concrete into structural member joint area. The purpose of this study is to change ACI 349 Code for using the large-size(57mm) and high-strength(Gr.80) headed deformed bars instead of standard hooked bars in nuclear power plant concrete structures in order to solve the congestion problems.

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An Experimental Study on the Effects of Steel Fibers used at R/C Exterior Joints (철근 콘크리트 보-기둥 외측 접합부에 적용된 강섬유의 효과에 관한 실험연구)

  • Choi, Ki-Bong;Oh, Jong-Han;Kim, Jae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.2 no.3
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    • pp.188-193
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    • 1998
  • An experimental study was performed on the pull-out behavior of 90-deg standard hooks from exterior beam-column connections. The effects of lateral confinement and fiber reinforcement of joint area were investigated. It was concluded ; (1) Substitution of the transverse column (confining) reinforcement with steel fibers at the joint region effectively reduces the extent of cracking in exterior joints caused by pull-out of hooked bars; and (2) The strength and ductility of hooked bars under pull-out forces are positively influenced by substituting the conventional confining reinforcement of exterior joints with steel fibers. Application of steel fibers to exterior joints seems to be an effective technique for improving the anchorage conditions of hooked bars, and also for reducing the congestion of reinforcement in exterior beam-column connections.

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Code Change for Using Large-Sized/High-Strength Headed Deformed Bars in Nuclear Power Plant Structures (대구경/고강도 확대머리철근의 원전구조물 사용을 위한 코드개정방안 연구)

  • Lee, Byung-Soo;Bang, Chang-Joon;Kim, Suck-Chul;Lim, Sang-Joon
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2014.05a
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    • pp.80-81
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    • 2014
  • Generally significant reinforcement is used for nuclear power plant structures and may cause potential problems when concrete is poured. In particular pouring concrete into structural member joint area is more difficult than other areas since the joint area is very congested due to hooked bars, embedded plates, and other reinforcements. The purpose of this study is to solve the problem by applying high-strength(ASTM A615 Gr. 75/80) bars. In addition large-sized(#14 & #18) headed deformed bar could be used as alternative of standard hooked bars to relieve the congestion to some extent. In order to apply headed deformed bars to nuclear power plant structures effectively, the large-sized diameter bars and the high-strength bars shall be used as thick as clear cover thickness 1". Therefore, test results were obtained by taking bar size, yield strength, and clear cover thickness as variables.

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Code Change for using the High-Strength(550 MPa) Headed Deformed Bars of Large-Sized Diameter(57 mm) in Concrete Containments (대구경(57 mm) 및 고강도(550 MPa) 확대머리 철근의 콘크리트 격납구조물 적용을 위한 코드개정에 관한 연구)

  • Lee, Byung-Soo;Lim, Sang-Jun;Yun, Hyun-Do
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.6
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    • pp.147-161
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    • 2017
  • Generally, significant amount of reinforcements are used in nuclear power plant structures and it may cause several potential problems during the construction. In particular, it is more difficult to pour concrete into structural member joint area than other areas because of the significant congestion of the joint area due to a lot of hooked bars, embedded materials, and other reinforcements. The purpose of this study is to solve these problems due to the reinforcement congestion by using the high-strength(ASTM A615 Gr.80) headed deformed bars of large-sized diameter(43 mm & 57 mm) in nuclear power plant structures as a alternative of standard hooked bars. In order to use headed deformed bars effectively, It is necessary to find the method how to relax limits on their use while maintaining or improving the anchorage capacity. Therefore, this study will analyze the results of tests planned to evaluate the influence of the restricted variables, such as bar size, yield strength, clear cover thickness.

Behavior of Mechanical Anchorage of Bars Embedded in Concrete Blocks

  • You, Young-Chan;Park, Keun-Do;Kim, Keung-Hwan;Lee, Li-Hyung
    • KCI Concrete Journal
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    • v.14 no.2
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    • pp.86-91
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    • 2002
  • This paper presents an experimental study to investigate the behavior of mechanical anchorage of reinforcing bars in concrete members. Three kinds of mechanical anchorage which are a kind of headed reinforcements are considered in this study. Total seven specimens were prepared to consider the effects of anchoring methods (Type A, Type B and Type C) and anchorage lengths of the reinforcing bars (14 $d_{b}$, 12 $d_{b}$, 9 $d_{b}$). Pullout tests conforming to ASTM were carried out to assess the effects of several variables on anchoring strength of bars. Based on the test results, it was concluded that the behavior of the specimen anchored by the mechanical anchorage with the anchor-age length of 12 $d_{b}$, is as good as, or better than that of the specimen anchored by 90-degree standard hook.rd hook.

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Study on the Effect on the Development Design of Headed Deformed Bars by change of ACI 318-19 (ACI 318-19 변경에 따른 확대머리철근 정착설계의 영향분석)

  • Lee, Byung Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2019.11a
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    • pp.110-111
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    • 2019
  • In ACI 318-19 published recently, the conditions and development length equation to use the headed deformed bars were changed considerably. Although the use of the larger-diameter(No.14 and 18) headed deformed bars isn't yet permitted, the use of the high strength(80,000psi) headed deformed bars is permitted and the effect of bar-diameter($d_b$) on the development length is increased considerably. Therefore, structures using larger-diameter headed deformed bars will be expected to be affected by this code change. We will study the effect of the code change on the development design and find out the design optimization method to minimize the effect of the changed conditions and development length equation.

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An Experimental Study of Reinforced Concrete Beams with Closely-Spaced Headed Bars

  • Lam, Kah Mun;Kim, Woo-Suk;Van Zandt, Michael;Kang, Thomas H.K.
    • International Journal of Concrete Structures and Materials
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    • v.5 no.2
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    • pp.77-85
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    • 2011
  • The use of headed bars as opposed to standard 90- or 180-degree hooked bars in beam ends, beam-column joints or other steel congested areas for anchorage and bond has become more favorable due to the fact that steel congestion is often created by large bend diameters or crossties. This research mainly focuses on evaluating the code provisions regarding the use of headed bars. Nine simply supported rectangular concrete beams with headed longitudinal reinforcement were tested under a four-point monotonic loading system. The design clear spacing, which varies from 1.5 to 4.25 times the bar diameter, was the only parameter for the experimental investigation. The test results showed that the closely-spaced headed bars were capable of developing to full yield strength without any severe brittle concrete breakout cone or pullout failure. Bond along the bar was not sufficient due to the early loss of concrete integrity. However, the headed bars were effective for anchorage with no excessive moment capacity reduction. This implies that the clear spacing of about 2 times the bar diameter for headed bars may be reasonable to ensure the development of specified yield strength of headed bars and corresponding member design strength.