• Title/Summary/Keyword: strut-and-tie

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Design of End Diaphragms in PSC Box Girder Bridges Using a Strut-and-Tie Model (스트럿-타이 모델을 이용한 PSC 박스거더 교량의 End Diaphragm의 설계 연구)

  • 이창훈;윤영수;이만섭;김병석
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.961-966
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    • 2003
  • In recent, the design of diaphragm which is representative disturbed region in PSC box girder bridge have been performed according to the empirical method or beam theory. But, these methods couldn't be described the behavior of the end diaphragm, and placed reinforcements accurately. As the compressive stress transferred by the web concentrated on the lower parts of diaphragm, it was demonstrated that the basic assumption of 2-D strut-and-tie model for the diaphragm that the compressive stress acts on the upper parts of the diaphragm is wrong. Meanwhile, in this research, after analyzing the variables of end diaphragm, the 2-D strut-and-tie models appropriate to each cases are proposed. And, the problems of 2-D strut-and-tie model were analyzed, so 3-D strut-and-tie model is proposed as well. There is no codes which include the demonstration of safety of 3-D strut-and-tie model. Hence, for nodes, the stresses at the elements which included the singular node in strut-and-tie model were investigated using the finite element analysis. And, the stress states of strut has one direction, so effective stresses were considered at the stage, dimensioning of the model. From the results, 3-D strut-and-tie model could predict the behavior of end diaphragm accurately, and design of reinforcement could be performed economically.

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Design of Anchorage Zone in Prestressed Concrete Structure Using Nonlinear Strut and Tie Model (비선형 스트럿-타이 모델에 의한 PC 구조물의 정착부 설계)

  • 배한옥;변근주;송하원
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.392-397
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    • 1997
  • In this paper, design and analysis of anchorage zone in prestressed concrete structure using nonlinear strut and tie model is presented. Nonlinear strut and tie model is an analysis and design model which constructs strut and tie model based on nonlinear analysis considering the nonlinear behavior of concrete. Based on the nonlinear strut and tie model, the analysis and design are performed for the anchorage zone having singular concentric tendons, singular eccentric tendons and multiple tendons, respectively. For verification of the model, comparisons are made with experimental results as well as results by linear strut and tie models. from the comparisons, it is shown that the design of the anchorage zone by the nonlinear model is still economical without loosing the degree of safety and the prediction of the ultimate load by the nonlinear model gives better accuracy than by the linear one.

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Evaluation of Shear Strength of RC Beams using Strut-and-Tie Model (스트럿-타이 모델을 이용한 세장한 철근콘크리트 부재의 강도평가)

  • Park, Hong-Gun;Eom, Tae-Sung;Park, Chong-Chul
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.271-274
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    • 2005
  • Existing strut-and-tie model cannot be applied to analysis of slender beams without shear reinforcement because shear transfer mechanism is not formed. In the present study, a new strut-and-tie model with rigid joint was developed. Basically, concrete strut is modeled as a frame element which can transfer shear force (or moment) as well as axial force. Employing Rankine failure criterion, failure strength due to shear-tension and shear-compression developed in compressive concrete strut was defined. For verification, various test specimens were analyzed and the results were compared with tests. The proposed strut-and-tie model predicted shear strength and failure displacement with reasonable precision, addressing the design parameters such as shear reinforcement, concrete compressive strength, and shear span ratio.

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Modeling of non-seismically detailed columns subjected to reversed cyclic loadings

  • Tran, Cao Thanh Ngoc
    • Structural Engineering and Mechanics
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    • v.44 no.2
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    • pp.163-178
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    • 2012
  • A strut-and-tie model is introduced in this paper to predict the ultimate shear strength of non-seismically detailed columns. The validity and applicability of the proposed strut-and-tie model are evaluated by comparison with available experimental data. The model was developed based on visible crack patterns observed on the test specimens. The concrete contribution is integrated into the strut-and-tie model through a concept of equivalent transverse reinforcement. To further validate the model a full-scale non-seismically detailed reinforced concrete column was tested to investigate its seismic behavior. The specimen was tested under the combination of a constant axial load, $0.30f_c{^{\prime}}A_g$ and quasi-static cyclic loadings simulating earthquake actions. Quasi-static cyclic loadings simulating earthquake actions were applied to the specimen until it could not sustain the applied axial load. The analytical results reveal that the strut-and-tie method is capable of modeling to a satisfactory accuracy the ultimate shear strength of non-seismically detailed columns subjected to reserved cyclic loadings.

Strut-and-tie model of deep beams with web openings - An optimization approach

  • Guan, Hong
    • Structural Engineering and Mechanics
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    • v.19 no.4
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    • pp.361-379
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    • 2005
  • Reinforced concrete deep beams have useful applications in tall buildings and foundations. Over the past two decades, numerous design models for deep beams were suggested. However even the latest design manuals still offer little insight into the design of deep beams in particular when complexities exist in the beams like web openings. A method commonly suggested for the design of deep beams with openings is the strut-and-tie model which is primarily used to represent the actual load transfer mechanism in a structural concrete member under ultimate load. In the present study, the development of the strut-and-tie model is transformed to the topology optimization problem of continuum structures. During the optimization process, both the stress and displacement constraints are satisfied and the performance of progressive topologies is evaluated. The influences on the strut-and-tie model in relation to different size, location and number of openings, as well as different loading and support conditions in deep beams are examined in some detail. In all, eleven deep beams with web openings are optimized and compared in nine groups. The optimal strut-and-tie models achieved are also compared with published experimental crack patterns. Numerical results have shown to confirm the experimental observations and to efficiently represent the load transfer mechanism in concrete deep beams with openings under ultimate load.

Direct Inelastic Design of Reinforced Concrete Members Using Strut-and-Tie Model (스트럿-타이 모델을 이용한 철근콘크리트 부재의 직접 비탄성 설계)

  • Eom, Tae-Sung;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.20 no.3
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    • pp.345-356
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    • 2008
  • In the previous study, direct inelastic strut-and-tie model (DISTM) was developed to perform inelastic design of reinforced concrete members by using linear analysis for their secant stiffness. In the present study, for convenience in design practice, the DISTM was further simplified so that inelastic design of reinforced concrete members can be performed by a run of linear analysis, without using iterative calculations. In the simplified direct inelastic strut-and-tie model (S-DISTM), a reinforced concrete member is idealized with compression strut of concrete and tension tie of reinforcing bars. For the strut and tie elements, elastic stiffness or secant stiffness is used according to the design strategy intended by engineer. To define the failure criteria of the strut and tie elements, concrete crushing and reinforcing bar fracture were considered. The proposed method was applied to inelastic design of various reinforced concrete members including deep beam, coupling beam, and shear wall. The design results were compared with the properties and the deformation capacities of the test specimens.

Shear Design of Reinforced Concrete Shear Walls with Openings using Strut-and-Tie Models (스트럿-타이 모델을 이용한 개구부를 갖는 전단벽의 전단 설계)

  • Hong, Sung-Gul;Jang, Sang-Ki
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.244-247
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    • 2004
  • This study proposes the design method of the shear walls with openings using strut-and-tie models. Strut-and-tie models are constructed for opening near the middle of the wall and for opening near a wall boundary. These enables an admissible load path for the horizontal earthquake force. These models consider the size and position of opening effectively. Each model is suitable for the seismic response corresponding with lateral forces in a given direction to be considered. The proposed models are good agreements with nonlinear finite element analysis(DIANA) results.

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Concepts on Deformation Dependent Strut-and-Tie Models (변형을 고려한 스트럿-타이 모델)

  • Hong, Sung-Gul;Jang, Sang-Ki
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.209-212
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    • 2005
  • This paper presents, basic concepts on deformation models for D-regions critical to shear. Strut-and-tie models are used to construct for deformation estimation at yielding and ultimate deformation. A generic: strut-and-tie model is proposed to investigate deformation patterns and failure mode identification. Superposition of the basic models enables us to explain deformation limits of arch action and truss action. Displacement at yielding is assessed by consideration of deformation of reinforcing steel only while the ultimate displacement is calculated by limits of ultimate strain of concrete in compression and failure mechanisms.

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Strut-and-Tie Models for RC Flexural Members under Cyclic Loading (스트럿-타이 모텔을 이용한 RC 휨부재의 주기적 거동에 관한 연구)

  • 이수곤;홍성걸
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.453-458
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    • 2001
  • This paper presents the procedure to find the hysteresis loop of RC member using a modified strut-and-tie model. The forces and displacements at critical points, that are initial yielding point, target displacement point, unloading elastic limit, and reloading point after pinching, are investigated with the strut-and-tie models. Using bond-slip relationship, the elastic behavior of tie element is determined. The plastic flow behavior after flexural yielding is expressed by changing the location of longitudinal strut. Determination of pinching effect completes the initial hysteresis loop, assuming that the behavior of the opposite direction is symmetrical form.

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New strut-and-tie-models for shear strength prediction and design of RC deep beams

  • Chetchotisak, Panatchai;Teerawong, Jaruek;Yindeesuk, Sukit;Song, Junho
    • Computers and Concrete
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    • v.14 no.1
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    • pp.19-40
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    • 2014
  • Reinforced concrete deep beams are structural beams with low shear span-to-depth ratio, and hence in which the strain distribution is significantly nonlinear and the conventional beam theory is not applicable. A strut-and-tie model is considered one of the most rational and simplest methods available for shear strength prediction and design of deep beams. The strut-and-tie model approach describes the shear failure of a deep beam using diagonal strut and truss mechanism: The diagonal strut mechanism represents compression stress fields that develop in the concrete web between diagonal cracks of the concrete while the truss mechanism accounts for the contributions of the horizontal and vertical web reinforcements. Based on a database of 406 experimental observations, this paper proposes a new strut-and-tie-model for accurate prediction of shear strength of reinforced concrete deep beams, and further improves the model by correcting the bias and quantifying the scatter using a Bayesian parameter estimation method. Seven existing deterministic models from design codes and the literature are compared with the proposed method. Finally, a limit-state design formula and the corresponding reduction factor are developed for the proposed strut-andtie model.