• Title/Summary/Keyword: 콘크리트 소성

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Nonlinear Analysis of Reinforced Concrete Members using Plasticity with Multiple Failure Criteria (다중 파괴기준의 소성모델을 이용한 철근콘크리트부재의 비선형 해석)

  • 박홍근
    • Magazine of the Korea Concrete Institute
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    • v.7 no.5
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    • pp.145-154
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    • 1995
  • Concrete has two different failure mechanisms : compressive crushing and tensile cracking. Concrete models should use the two different failure criteria to analyze the inelastic behavior of concrete including multiaxial crushing and tensile cracking. Concrete models used in this study are based on plasticity with multiple failure criteria of compressive crushing and tensile cracking. For tensile cracking behavior, two different plasticity models are investigated. The* ,e are rotating-crack and fixed-crack plasticity models, classified according to idealization of crack 0rientat:ions. The material models simplify inelastic behavior of concrete for plane stress problenls. The material models are used for the finite element anlaysis. Analytical results are compared with several experiments of reinforced concrete member. The advantages and disadva.ntages of rotating-crack and fixed -crack plasticity models are discussed.

Evaluation of Plastic Rotational Capacity Based on Material Characteristics in Reinforced Concrete Flexural Members (재료 특성에 기반한 철근콘크리트 휨부재의 소성회전능력 산정)

  • Choi, Seung-Won;Kim, Woo
    • Journal of the Korea Concrete Institute
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    • v.22 no.6
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    • pp.825-832
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    • 2010
  • Although a critical section reaches its flexural strength in reinforced concrete structures, the structure does not always fail because moment redistribution occurs during the formation of plastic hinges. Inelastic deformation in a plastic hinge region results in plastic rotation. A plastic hinge mainly depends on material characteristics. In this study, a plastic hinge length and plastic rotation are evaluated using the flexural curvature distribution which is derived from the material models given in Eurocode 2. The influence on plastic capacity the limit values of the material model used, that is, ultimate strain of concrete and steel and hardening ratio of steel(k), are investigated. As results, it is appeared that a large ultimate strain of concrete and steel is resulting in large plastic capactiy and also as a hardening ratio of steel increases, the plastic rotation increases significantly. Therefore, a careful attention would be paid to determine the limit values of material characteristics in the RC structures.

3-D Concrete Model Using Non-associated Flow Rule in Dilatant-Softening Region of Multi-axial Stress State (3차원 솔리드요소 및 비상관 소성흐름 법칙을 이용한 콘크리트의 응력해석)

  • Seong, Dae Jeong;Choi, Jung Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.2
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    • pp.193-200
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    • 2008
  • Cohesive and frictional materials such as concrete and soil are pressure dependent. In general, failure criterion for such materials inclined with respect to positive hydrostatic axis in Haigh-Westergaard stress space. Consequently, inelastic volumetric strain always positive with associated flow rule. In this study, to overcome this shortcoming, non-associated flow rule which controls volumetric component of plastic flow is adopted. Numerical analysis based on a constitutive model using nonuniform hardening plasticity with five parameter failure criterion and non-associated flow rule has conducted to predict concrete behavior under multi-axial stress state and verified with experimental result.

A Numerical Study on the Characteristics of Plastic Shrinkage Cracking on Concrete Slab with Sequential Placement (분할타설되는 콘크리트 슬래브의 소성수축균열 특성에 대한 해석적 연구)

  • Kwak, Hyo-Gyoung;Ha, Soo-Jun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4A
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    • pp.795-808
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    • 2006
  • In this paper, an analytical method which can predict the occurrence of plastic shrinkage cracking on concrete slabs with sequential placement is proposed on the basis of the numerical model introduced in the previous study. The influence of many design variables on plastic shrinkage cracking such as the number of layers and the time interval between layers is quantitatively analyzed through parametric studies using the analytical method. In advance, two equations are introduced to take into account the effect of sequential placement on the plastic shrinkage cracking of concrete slab; The first one is to calculate the time at which the surface of concrete slab begins to dry, and the second one is to determine the critical time interval to prevent the surface drying of previously placed concrete layers. The timing of curing and the sequence of concrete placement, which are important for the prevention of plastic shrinkage cracking, can be effectively planned using the introduced both equations without any rigorous analysis.

Model for Flow Analysis of Fresh Concrete Using Particle Method with Visco-Plastic Flow Formulation (점소성 유동 입자법에 의한 굳지 않은 콘크리트의 유동해석 모델)

  • Cho, Chang-Geun;Kim, Wha-Jung;Choi, Yeol
    • Journal of the Korea Concrete Institute
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    • v.20 no.3
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    • pp.317-323
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    • 2008
  • In the current study, A model for the flow analysis of fresh and highly flowable concrete has been developed using a particle method, the moving particle semi-implicit (MPS) method. The phenomena on the flow of concrete has been considered as a visco-plastic flow problem, and the basic governing equation of concrete particle dynamics has been based on the Navier-Stokes equation in Lagrangian form and the conservation of mass. In order to formulate a visco-plastic flow constitutive law of fresh concrete, concrete is modeled as a highly viscous material in the state of non-flow and as a visco-plastic material in the state of flow after reaching the yield stress of fresh concrete. A flow test of fresh concrete in the L-box was simulated and the predicted flow was well matched with the experimental result. The developed method was well showed the flow motion of concrete particles because it was formulated to be based on the motion of visco-plastic fluid dynamics.

Plasticity Model for Directionality of Concrete Crack Damages (콘크리트 균열 손상의 방향성을 고려한 다중파괴기준 소성 모델)

  • Kim, Jae-Yo;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.19 no.5
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    • pp.655-664
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    • 2007
  • The inherent characteristic of concrete tensile cracks, directional nonlocal crack damage, causes so-called rotating tensile crack damage and softening of compressive strength. In the present study, a plasticity model was developed to describe the behavior of reinforced concrete planar members In tension-compression. To describe the effect of directional nonlocal crack damage, the concept of microplane model was combined with the plasticity model. Unlike existing models, in the proposed model, softening of compressive strength as well as the tensile crack damage were defined by the directional nonlocal crack damage. Once a tensile cracking occurs, the microplanes of concrete are affected by the nonlocal crack damage. In the microplanes, microscopic tension and compression failure surfaces are calculated. By integrating the microscopic failure surfaces, the macroscopic failure surface is calculated. The proposed model was implemented to finite element analysis, and it was verified by comparisons with the results of existing shear panel tests.

Finite Element Mesh Dependency in Nonlinear Earthquake Analysis of Concrete Dams (콘크리트 댐의 비선형 지진해석에서의 유한요소망 영향)

  • 이지호
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.637-644
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    • 2001
  • A regularization method based on the Duvaut-Lions viscoplastic scheme for plastic-damage and continuum damage models, which provides mesh-independent and well-posed solutions in nonlinear earthquake analysis of concrete dams, is presented. A plastic-damage model regularized using the proposed rate-dependent viscosity method and its original rate-independent version are used for the earthquake damage analysis of a concrete dam to analyze the effect of the regualarization and mesh. The computational analysis shows that the regularized plastic-damage model gives well-posed solutions regardless mesh size and arrangement, while the rate-independent counterpart produces mesh-dependent ill-posed results.

An Analytical Investigation on the Ultimate Strength of Concrete-Filled Steel Tube Columns using Elasto-Plastic Large Deformation Analysis (탄소성 대변형 해석을 이용한 콘크리트 충전강관(CFT) 기둥의 극한강도에 관한 해석적 연구)

  • Jang, Gab-Chul;Chang, Kyong-Ho
    • Journal of Korean Association for Spatial Structures
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    • v.7 no.6
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    • pp.69-74
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    • 2007
  • Recently, to improve performance and strength of circular steel columns, application of concrete-filled steel tube(CFT) type are gradually increased. To accurately predict the plastic design of concrete-filled steel tube columns, a plasticity model is required which can be describe large deformation behavior of concretes and steels. In this study, elastic-plastic large deformation analysis is developed by using the plasticity model of structural steels, and accurate and validity of the developed program is verified by comparing between the experiment and the analysis for concrete-filled steel tube column. In concrete-filled steel tube columns, influence of initial deflection on ultimate strength behavior is investigated by using developed program.

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Material Nonlinear Analysis of RC Beams Based on Moment-Curvature Relations (모멘트-곡률 관계에 기초한 철근콘크리트 보의 재료비선형 해석)

  • 곽효경;김지은
    • Computational Structural Engineering
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    • v.11 no.4
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    • pp.295-307
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    • 1998
  • 철근콘크리트 보에 대해서 인장강화효과의 소성힌지길이를 고려한 재료비선형 해석을 수행하였다. 비선형 해석에서 자유도가 많은 대형구조물에 적용시키기에는 많은 제약이 따르는 복잡한 층상해석기법을 사용하는 대신 단면해석을 통해 미리 구성된 모멘트-곡률 관계를 이용하였으며, 유한요소해석에서 사용요소의 크기에 따른 수치해석상의 오차를 줄이기 위해 인장강화효과와 소성힌지길이 개념을 도입하였다. 마지막으로 제안된 해석 알고리즘의 타당성을 검증하기 위하여 해석결과와 실험결과간의 상호 관계를 비교, 분석하였다.

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Deformability of RC Beam-Column Assembles (철근콘크리트 보-기둥 접합부의 연성능력)

  • Lee, Jung-Yoon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.193-196
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    • 2008
  • This paper proposes a method to predict the ductility capacity of reinforced concrete beam-column joints failing in shear after the formations of plastic hinges at both ends of the adjacent beams. The current design code divides joints into two categories: Type 1 for structures in non seismically hazard area and Type 2 in seismically hazard area. While there are many researches related to joint shear strength in Type 1, those in regard to joint ductility capacity of Type 2 are scarce. This paper classified the ductility capacity of beam-column joints into column, joint panel, and beam deformability. Since a brittle failure such as shear or bond failure in the columns must be avoided, column deformability was calculated by elastic analysis. The plastic hinges of the adjacent beams affect joint deformability. Therefore, the prediction of joint deformability was calculated with consideration to the degradation of the diagonally compressed concrete due to the strain penetration.

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