• Title/Summary/Keyword: Strut-Tie

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Effective Strengths of Concrete Struts in Strut-Tie Models of Reinforced Concrete Deep Beams (철근콘크리트 깊은 보 스트럿-타이 모델의 콘크리트 스트럿의 유효강도)

  • Chae, Hyun Soo;Yun, Young Mook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.6
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    • pp.2195-2209
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    • 2013
  • The effective strength of concrete struts must be determined accurately for the reliable strut-tie model analysis and design of structural concrete. In this study, the equations of the effective strength, which are useful for the three types of determinate and indeterminate strut-tie models of reinforced concrete deep beams employed in current design codes, are proposed. The effects of shear span-to-effective depth ratio, compressive strength of concrete, and flexural and shear reinforcement ratios are reflected in the development of the proposed equations. To examine the appropriateness of the proposed equations, the strengths of 241 reinforced concrete deep beams, all tested to shear failure, are evaluated by using the three types of strut-tie models with the existing and proposed equations.

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.

3-Dimensional Strut-Tie Model Analysis and Design of Structural Concrete (콘크리트 구조부재의 3차원 스트럿-타이 모델 해석 및 설계)

  • Yun, Young Mook;Park, Jung Woong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.3A
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    • pp.411-419
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    • 2006
  • In this study, a new approach employing 3-dimensional strut-tie models for analysis and design of 3-dimensional structural concrete with disturbed regions that are not properly occupied by current design codes is proposed. In addition, a computer graphics program for the practical application of the approach is developed. The approach adopts a grid strut-tie model to exclude the subjectivity in the selection of strut-tie model and evaluates the effective strength of concrete strut by considering the 3-dimensional failure criteria of concrete and the deviation angles between the struts and compressive principal stress trajectories. To verify the appropriateness of the approach, nine pile caps tested to failure are analyzed and a bridge pier is designed. The analysis and design results are compared with those obtained by several different methods.

Numerical method for the strength of two-dimensional concrete struts

  • Yun, Y.M.
    • Computers and Concrete
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    • v.28 no.6
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    • pp.621-634
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    • 2021
  • For the reliable strut-and-tie model (STM) design of disturbed regions of concrete members, structural designers must accurately determine the strength of concrete struts to check the strength conditions of a selected STM el and the anchorage of reinforcing bars in nodal zones. In this study, the author proposed a consistent numerical method for strut strength, applicable to all two-dimensional STMs. The proposed method includes the effects of a biaxial stress state associated with tensile strains in reinforcing bars crossing a strut, deviation angle between strut orientation and compressive principal stress flow, and degree of confinement provided by reinforcement. The author examined the method's validity through the STM prediction of the ultimate strengths of 517 reinforced concrete (RC) deep beams, 24 RC panels, and 258 RC corbels, all tested to failure.

Deformation-based Strut-and-Tie Model for flexural members subject to transverse loading

  • Hong, Sung-Gul;Lee, Soo-Gon;Hong, Seongwon;Kang, Thomas H.K.
    • Computers and Concrete
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    • v.18 no.6
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    • pp.1213-1234
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    • 2016
  • This paper describes a deformation-based strut-and-tie model for the flexural members at post-yield state. Boundary deformation conditions by flexural post-yield response are chosen in terms of the flexural bar strains as the main factor influenced on the shear strength. The main purpose of the proposed model is to predict the shear capacities of the flexural members associated with the given flexural deformation conditions. To verify the proposed strut-and-tie model, the estimated shear strengths depending on the flexural deformation are compared with the experimental results. The experimental data are in good agreement with the values obtained by the proposed model.

Determination of strut efficiency factor for concrete deep beams with and without fibre

  • Sandeep, M.S.;Nagarajan, Praveen;Shashikala, A.P.;Habeeb, Shehin A.
    • Advances in Computational Design
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    • v.1 no.3
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    • pp.253-264
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    • 2016
  • Based on the variation of strain along the cross section, any region in a structural member can be classified into two regions namely, Bernoulli's region (B-region) and Disturbed region (D-region). Since the variation of strain along the cross section for a B-region is linear, well-developed theories are available for their analysis and design. On the other hand, the design of D-region is carried out based on thumb rules and past experience due to the presence of nonlinear strain distribution. Strut-and-Tie method is a novel approach that can be used for the analysis and design of both B-region as well as D-region with equal importance. The strut efficiency factor (${\beta}_s$) is needed for the design and analysis of concrete members using Strut and Tie method. In this paper, equations for finding ${\beta}_s$ for bottle shaped struts in concrete deep beams (a D-region) with and without steel fibres are developed. The effects of transverse reinforcement on ${\beta}_s$ are also considered. Numerical studies using commercially available finite element software along with limited amount of experimental studies were used to find ${\beta}_s$.

Direct Inelastic Strut-Tie Model Using Secant Stiffness (할선강성을 이용한 직접 비탄성 스트럿-타이 모델)

  • Park Hong-Gun;Kim Yun-Gon;Eom Tae-Sung
    • Journal of the Korea Concrete Institute
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    • v.17 no.2 s.86
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    • pp.201-212
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    • 2005
  • A new strut-tie model using secant stiffness, Direct Inelastic Strut-Tie Model, was developed. Since basically the proposed design method uses linear analysis, it is convenient and stable in numerical analysis. At the same time, the proposed design method can accurately estimate the inelastic strength and ductility demands of struts and ties because it can analyzes the inelastic behavior of structure using iterative calculations for secant stiffness. In the present study, the procedure of the proposed design method was established, and a computer program incorporating the proposed method was developed. Design examples using the proposed method were presented, and its advantages were highlighted by the comparison with the traditional strut-tie model. The Direct Inelastic Strut-Tie Model, as an integrated analysis/design method, can directly address the design strategy intended by the engineer to prevent development of macro-cracks and brittle failure of struts. Since the proposed model can analyze the inelastic deformation, indeterminate strut-tie model can be used. Also, since the proposed model controls the local deformations of struts and ties, it can be used as a performance-based design method for various design criteria.

Strut-Tie Model Approach Associated with 3-Dimensional Grid Elements for Design of Structural Concrete - (II) Validity Evaluation (3차원 격자요소를 활용한 콘크리트 구조부재의 스트럿-타이 모델 설계 방법 - (II) 타당성 평가)

  • Kim, Byung Hun;Yun, Young Mook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.2
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    • pp.437-446
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    • 2014
  • In this study, the ultimate strengths of 13 slab-column joints and 51 torsional beams were evaluated to verify the validity of the strut-tie model approach presented in the companion paper. In addition, the design of the bridge pier subjected to multiple load combinations with longitudinal and lateral loads was conducted. The analysis results were compared with those by the provisions of BS 8110, ACI 318, and AASHTO-LRFD. The design results of the bridge pier were also compared with those by the provisions of ACI 318's sectional design method and AASHTO-LRFD's strut-tie model method.

Analysis of reinforced concrete corbel beams using Strut and Tie models

  • Parol, Jafarali;Al-Qazweeni, Jamal;Salam, Safaa Abdul
    • Computers and Concrete
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    • v.21 no.1
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    • pp.95-102
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    • 2018
  • Reinforced concrete corbel beams (span to depth ratio of a corbel is less than one) are designed with primary reinforcement bars to account for bending moment and with the secondary reinforcement placed parallel to the primary reinforcement (shear stirrups) to resist shear force. It is interesting to note that most of the available analytical procedures employ empirical formulas for the analysis of reinforced concrete corbels. In the present work, a generalized and a simple strut and tie models were employed for the analysis of reinforced corbel beams. The models were benchmarked against experimental results available in the literature. It was shown here that increase of shear stirrups increases the load carrying capacity of reinforced concrete corbel beams. The effect of horizontal load on the load carrying capacity of the corbel beams has also been examined in the present paper. It is observed from the strut and tie models that the resistance of the corbel beam subjected to combined horizontal and vertical load did not change with increase in shear stirrups if the failure of the corbel is limited by concrete crushing. In other words, the load carrying capacity was independent of the horizontal load when failure of the beam occurred due to concrete crushing.

Analysis of PSC Box Girder Anchorage Zone using FEM and 2D SUB-3D STM Approach (유한요소법 및 유사 3 차원 스트릿-타이 모델 방법을 이용한 PSC 박스거더 정착부의 해석)

  • Yun, Young-Mook;Kim, Seung-Eock;Oh, Jin-Woo;Park, Jung-Woong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.4 no.2
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    • pp.113-129
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    • 2000
  • This study evaluates the behavior and strength of an anchorage zone of the prestressed concrete box girder bridge on the Kyungboo highway railroad using the 2D SUB-3D STM approach and a linear elastic finite element analysis. The 2D SUB-3D STM approach utilizes several two-dimensional sub strut-tie models that represent the compressive and tensile stress flows of each projected plane of the three-dimensional structural concrete in the selection of a three dimensional strut-tie model, evaluation of the effective strengths of the concrete struts, and verification of the geometric compatibility condition and bearing capacity of the critical nodal zones in the selected three-dimensional strut-tie model. The finite element analysis uses an 8-node brick element and the longitudinal prestressing force is considered as the equivalent nodal force. Analysis results show that the 2D SUB-3D STM approach and linear elastic finite element method can be effectively applied to the analysis and design of three-dimensional structural concrete including a prestressed concrete box girder anchorage zone.

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