• Title/Summary/Keyword: minimum shear reinforcement

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Rational Approach for Minimum Shear and Torsion Reinforcement (전단과 비틀림의 최소 철근비에 대한 이론적 접근)

  • 이민섭;홍성걸
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.445-448
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    • 1999
  • The minimum shear and torsional reinforcement provisions in ACI 318-95 are still empirical. This paper describes the derivation of a rational approach for minimum shear and torsional reinforcement in beams so as to preclude brittle failure in shear and torsion. This is ensured by specifying that the beam's ultimate capacity of shear and torsion should be greater than its cracking shear and torsion. The formula presented herein for computing minimum shear and torsional reinforcement shows the need for modification of current provision for the minimum shear and torsion reinforcement.

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Minimum shear reinforcement ratio of prestressed concrete members for safe design

  • Park, Min-Kook;Lee, Deuck Hang;Ju, Hyunjin;Hwang, Jin-Ha;Choi, Seung-Ho;Kim, Kang Su
    • Structural Engineering and Mechanics
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    • v.56 no.2
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    • pp.317-340
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    • 2015
  • Design codes have specified the minimum shear reinforcement requirement for reinforced concrete (RC) and prestressed concrete (PSC) members to prevent brittle and premature shear failure. They are, however, very different from one another, and particularly, ACI318 code allows the required minimum shear reinforcement to be reduced in PSC members, compared to that in RC members, by specifying the additional equation for PSC members whose basis is not clear. In this paper, the minimum shear reinforcement ratio for PSC members was proposed, which can provide a sufficient reserved shear strength and deformation capacity. The proposed equation was also verified by the test results of PSC specimens lightly reinforced in shear, comparing to design codes and other proposed equations from previous studies.

Effects of Shear Span-to-depth Ratio and Tensile Longitudinal Reinforcement Ratio on Minimum Shear Reinforcement Ratio of RC Beams (전단경간비와 주인장철근비가 철근콘크리트 보의 최소전단철근비에 미치는 영향)

  • Lee Jung-Yoon;Kim Wook-Yeon;Kim Sang-Woo;Lee Bum-Sik
    • Journal of the Korea Concrete Institute
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    • v.16 no.6 s.84
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    • pp.795-803
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    • 2004
  • To prevent the shear failure that occurs abruptly with no sufficient warning, the minimum amount of shear reinforcement should be provided to reinforced concrete(RC) beams. The minimum amount of shear reinforcement of RC beams is influenced by not only compressive strength of concrete but also shear span-to-depth ratio and ratio of tensile longitudinal reinforcement. In this paper, 14 RC beams were tested in order to observe the influences of shear span-to-depth ratio, ratio of tensile longitudinal reinforcement, and compressive strength of concrete. The test results indicated that the rate of shear strength to the diagonal cracking strength of RC beams with the same amount of shear reinforcement increased as the ratio of tensile longitudinal reinforcement increased, while it decreased as the shear span-to-depth ratio increased. The observed test results were compared with the calculated results by the current ACI 318-02 Building Code and the proposed equation.

Web-shear capacity of prestressed hollow-core slab unit with consideration on the minimum shear reinforcement requirement

  • Lee, Deuck Hang;Park, Min-Kook;Oh, Jae-Yuel;Kim, Kang Su;Im, Ju-Hyeuk;Seo, Soo-Yeon
    • Computers and Concrete
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    • v.14 no.3
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    • pp.211-231
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    • 2014
  • Prestressed hollow-core slabs (HCS) are widely used for modern lightweight precast floor structures because they are cost-efficient by reducing materials, and have excellent flexural strength and stiffness by using prestressing tendons, compared to reinforced concrete (RC) floor system. According to the recently revised ACI318-08, the web-shear capacity of HCS members exceeding 315 mm in depth without the minimum shear reinforcement should be reduced by half. It is, however, difficult to provide shear reinforcement in HCS members produced by the extrusion method due to their unique concrete casting methods, and thus, their shear design is significantly affected by the minimum shear reinforcement provision in ACI318-08. In this study, a large number of shear test data on HCS members has been collected and analyzed to examine their web-shear capacity with consideration on the minimum shear reinforcement requirement in ACI318-08. The analysis results indicates that the minimum shear reinforcement requirement for deep HCS members are too severe, and that the web-shear strength equation in ACI318-08 does not provide good estimation of shear strengths for HCS members. Thus, in this paper, a rational web-shear strength equation for HCS members was derived in a simple manner, which provides a consistent margin of safety on shear strength for the HCS members up to 500 mm deep. More shear test data would be required to apply the proposed shear strength equation for the HCS members over 500 mm in depth though.

An Experimental Study to Predict Minimum Shear Reinforcement Ratio of RC Beams with Various Shear Span-to-Depth Ratios (전단경간비가 다른 철근콘크리트 보의 최소전단철근비 예측에 관한 실험적 연구)

  • 김욱연;김상우;이정윤
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.890-895
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    • 2003
  • The purpose of this experimental study is to investigate the influence of shear span-to-depth ratio on the minimum shear reinforcement ratio of reinforced concrete beams. In this study, 7 reinforced concrete beam specimens were tested. The parameters of experiment are shear span-to-depth ratio(a/d=2.0, 3.0, 4.0) and shear reinforcement ratio($p_v$=0%, 0.183%, and 0.233%). The section of all secimens was 350mm width and 450mm depth. The observed results were compared with the calculated results by the current ACI 318-02 Building Code and the proposed equation. The safety rate of the specimens, L5S2A, L5S3A, L5S4A, and L5S4P specimens were 1.80, 1.25, 1.38, and 1.56 respectively. The test results indicated that the shear behavior of reinforced concrete beams with the minimum shear reinforcement was influenced by the shear span-to-depth ratio.

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Evaluation of Minimum Shear Reinforcement Content of Reinforced Concrete Beams (철근콘크리트 보의 최소전단철근비 예측)

  • 윤성현;이정윤;김상우
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.253-258
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    • 2002
  • An evaluation equation of the minimum shear reinforcement content for reinforced concrete beams was theoretically proposed. The proposed equation takes into account the effects of compressive strength of concrete, longitudinal reinforcement content and shear span ratio. The proposed equation was compared with the current ACI 318-99 and CSA A23.3-94 codes.

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Assessment of Code Requirments on Minimum Shear Reinforcement in High-Strength RC Beams (RC 보의 강도증진에 따른 최소전단철근 규준의 적합성 평가에 관한 연구)

  • 윤영수;원종필;장일영
    • Proceedings of the Korea Concrete Institute Conference
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    • 1996.04a
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    • pp.289-294
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    • 1996
  • This paper persents the assessment of the minimum shear reinforcement requirements in normal, medium and high-strength reinforced concrete beams. Twelve shear tests were conducted on full-scale beam specimens having design concrete compressive strengths of 35, 70 and 100 MPa. Different amounts of minimum shear reinfrocement were investigated, including the amounts required by Korean Concrete Standard (KCI88), JCI86, ACI89 (revised 1992) and CSA94 standard. The performance of the different amounts of shear reinforcement are discussed in terms of the shear capacity, the ductility and the crack control at service load levels. An assessment of code provisions for minimum shear reinforcememt, and the prediction and comparison of the ultimate shear capacity are also presented.

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An Experimental Study on the Shear Strength of R.C Beam with Web reinforcement (전단보강이 된 철근콘크리트보의 전단강도에 관한 실험적 연구)

  • 이근광;홍기섭;신영수
    • Proceedings of the Korea Concrete Institute Conference
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    • 1993.10a
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    • pp.184-189
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    • 1993
  • This is an experimental investigation the shear behavior of reinforced concrete with stirrup of which stress ranges 0.0㎏/㎠ to 7.0㎏/㎠. Five rectangular beams which concrete strengths are 287㎏/㎠ and 380㎏/㎠, a/d=3, and main steel ratio equal to 1.96% was tested. Those were designed to fail in shear. The shear cracking load and failure load were measured and compared with ACI's equation and Zutty's proposed equation. The results are following : ACI equation and Zutty's equation are consertive. As the concrete compressive strength increased, reserved shear strength of beams with minimum web reinforcement decreases. According to increase of web reinforcement , the rate of increases of shear strength is decreased. The failure modes of specimen with minimum web reinforcement are shear compression failure which is reached after diagonal shear cracking.

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Evaluation on Shear Contribution of Steel Fiber Reinforced Concrete in Place of Minimum Shear Reinforcement (최소 전단철근 대용으로의 강섬유 콘크리트의 전단기여도 평가)

  • Kim, Chul-Goo;Park, Hong-Gun;Hong, Geon-Ho;Kang, Su-Min
    • Journal of the Korea Concrete Institute
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    • v.27 no.6
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    • pp.603-613
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    • 2015
  • In current design codes, minimum shear reinforcement is required for reinforced concrete flexural members, and the use of steel fiber reinforced concrete is permitted to replace the minimum shear reinforcements. In the present study, to estimate the effects of shear reinforcements and fibers on shear strength, simply supported beams were tested under transverse loading. The test results showed that the shear strength was significantly increased by the use of fibers. Particularly, the effect of fiber reinforced concrete was pronounced when high-strength concrete was used. The performance of fiber reinforced concrete for minimum shear reinforcement was evaluated using results of the present study and existing tests.

Numerical experimentation for the optimal design for reinforced concrete rectangular combined footings

  • Velazquez-Santilla, Francisco;Luevanos-Rojas, Arnulfo;Lopez-Chavarria, Sandra;Medina-Elizondo, Manuel;Sandoval-Rivas, Ricardo
    • Advances in Computational Design
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    • v.3 no.1
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    • pp.49-69
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    • 2018
  • This paper shows an optimal design for reinforced concrete rectangular combined footings based on a criterion of minimum cost. The classical design method for reinforced concrete rectangular combined footings is: First, a dimension is proposed that should comply with the allowable stresses (Minimum stress should be equal or greater than zero, and maximum stress must be equal or less than the allowable capacity withstand by the soil); subsequently, the effective depth is obtained due to the maximum moment and this effective depth is checked against the bending shear and the punching shear until, it complies with these conditions, and then the steel reinforcement is obtained, but this is not guaranteed that obtained cost is a minimum cost. A numerical experimentation shows the model capability to estimate the minimum cost design of the materials used for a rectangular combined footing that supports two columns under an axial load and moments in two directions at each column in accordance to the building code requirements for structural concrete and commentary (ACI 318S-14). Numerical experimentation is developed by modifying the values of the rectangular combined footing to from "d" (Effective depth), "b" (Short dimension), "a" (Greater dimension), "${\rho}_{P1}$" (Ratio of reinforcement steel under column 1), "${\rho}_{P2}$" (Ratio of reinforcement steel under column 2), "${\rho}_{yLB}$" (Ratio of longitudinal reinforcement steel in the bottom), "${\rho}_{yLT}$" (Ratio of longitudinal reinforcement steel at the top). Results show that the optimal design is more economical and more precise with respect to the classical design. Therefore, the optimal design presented in this paper should be used to obtain the minimum cost design for reinforced concrete rectangular combined footings.