• Title/Summary/Keyword: 항복 전단응력

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Numerical Analysis of Stress Regimes in and around Inactive and Active Fault Zones (비활성 그리고 활성 단층지역 내부와 주변에서의 응력장에 대한 수치적 분석)

  • Jeong, Woo-Chang;Song, Jai-Woo
    • Journal of the Korean Society of Hazard Mitigation
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    • v.1 no.1 s.1
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    • pp.117-125
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    • 2001
  • This paper presented the analysis of stress regimes in and around inactive and active fault zones. The stress regime in the vicinity of an existing inactive fault zone is dependent on the orientation of the fault with respect to the current stress field and the contrast between the elastic properties of the faulted rock and those of the surrounding rock. In the analysis of stress regimes around an active fault zone, if the yielding stress is exceeded during loading, the localized shearing in a fault zone will result in weakness with mean stresses in the fault becoming lower than those in the surrounding rock. It can be expected that such stress gradients will induce fluid flow towards the faults zone.

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A Study on Bingham Characteristics of Particle Dispersive Electro-Rheological Fluid (입자분산계 ER유체의 빙햄특성 고찰)

  • 장성철;이선의;김태형;박종근;염만오
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2000.10a
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    • pp.178-183
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    • 2000
  • Electrorheological(ER) effect on the dispersive system of polarizable fine powder/dielectric oil has been investigated. The electrical and rheological properties of zeolite and starch based ER fluid were reported. The ER fluids were constructed by mixing zeolite and starch power with two different dielectric oils. Yield stress of the fluids were measured on the couette cell type rheometer as a function of electric fields, particle concetrations, and temperatures. The electric field is applied by high voltage DC power supply. The outer cup is connected to positive electrode(+) and the bob becomes ground(-). And the temperatures the viscosity(or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to $200s^{-1}$ in 2 minutes.

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Bingham Charateristics of Electrorheological Fluid and Its Application to ER valve and ER Damper (전기유변유체의 빙햄특성과 밸브 및 댐퍼에의 응용)

  • 배종인
    • The Korean Journal of Rheology
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    • v.10 no.1
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    • pp.31-37
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    • 1998
  • 전기장이 인가되고 있는 유로를 유동하는 전기유변유체의 기본성질을 파악하기 위 한 실험 및 해석적 연구를 수행하여 빙햄유체로서의 유효성에 대해 알아보고 전기장과 유로 면 형상 및 진동유동으로 인한 영향에 대해 조사함으로써 ER밸브 및 ER대퍼로의 응용과 관련한 감쇄력 제어에 대해 검토하였다. 첫 번째 실험은 ER밸브의 높이가 2mm인 적극면이 평탄한것과 요철로 된 것을 사용하여 압력손실을 압력변환기로 측정함으로써 전기장 및 유 로형상에 대한 영향을 알아보았다. 압력손실 및 전단응력이 전기자세기와 함수관계를 가짐 을 알수 있었고 전기장세기와 유속의 변화시 손실계수에 의한 ER효과의 상이함이 확인되었 으며 레이놀즈수가 커지면 항복전단응력의 영향은 나타나지 않았다. 두 번째 실험은 실린더 를 정현파로 진동시켜 ER밸브에서 감쇠력제어가 가능한가를 알아보고 빙햄유체모델로 설계 된 ER댐퍼의 모델과 비교하였다. ER배르와 ER댐퍼의 수학적 모델을 시뮬레이션한 결과는 약간 벗어남이 보이기는 하나 실험결과와 일치하요 있다. 이것은 ER유체를 단순히 빙행유 체로 취급할수없으나 거시적으로는 빙햄유체로 취급할수 있음을 시사한다.

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Nonlinear Analysis of Stress-strain for RC Panel Subjected to Shear (순수전단이 작용하는 RC Panel의 응력-변형률 비선형해석)

  • Cha, Young-Gyu;Kim, Hak-Su
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.1
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    • pp.175-181
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    • 2010
  • The three truss models(equilibrium truss model, Mohr compatibility truss model, and the soften truss model) based on a rotating angle is called the rotating-angle model. The three rotating-angle models have a common weakness: they are incapable of predicting the so-called "contribution of concrete". To take into account this "contribution of concrete", the modern truss model(MCFT, STM) treats a cracked reinforced concrete element as a continuous material. By combining the equilibrium, compatibility, and the softened stress-strain relationship of concrete in biaxial state, MTM is capable of producing the nonlinear analysis of reinforced concrete structures composed of membrane element. In this paper, an efficient algorithm is proposed for the solution of proposed model incorporated with failure criteria. This algorithm is used to analyze the behavior of reinforced membrane element using the results of Hsu test.

A Study for Structural Behavior of R./C beams Strengthened with New Bonding Methods (보강재의 변형 부착에 따른 보의 구조적 거동)

  • 한만엽;송병표
    • Magazine of the Korea Concrete Institute
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    • v.10 no.3
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    • pp.197-208
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    • 1998
  • 최근들어 손상된 실구조물의 보강공법들이 적용,발전되어왔다. 가장 보편적으로 사용된공법이 강판과 탄소섬유를 이용한 공법이지만, 이론적인 배경과 적용기술이 아직은 정립되어었지 않은 상태이다. 강판보강의 경우 단부에서의 응력집중이 보강 효과를 결정짓는 가장 중요한 변수이므로, 본 연구에서는 이러한 응력집중을 완화하기 위하여 단부에 보강판과확대판을 부착하여 실험을 하였고, 탄소섬유 보강 실험에서는 다층 시공시 보강량을 조절하여 실험하였다. 실험 결과는 하중-처짐, 항복하중, 최대하중, 보강재의 전단응력의 분포와 보강재의 파괴양상을 분류하여 정리하였다. 실험을 통하여 강판 보강의 경우 본 연구에서 제안된 단부에서의 보강방법이 보강효과가 향상된 것을 확인하였고 탄소섬유 보강시에는 탄소섬유의 보강량을 조절함으로써 경제적인 설계와 시공이 가능한 것으로 나타났다.

Nonlinear Analysis of Shear Behavior on Pile-Sand Interface Using Ring Shear Tests (링전단시험을 이용한 말뚝 기초-사질지반 간 인터페이스 거동 분석)

  • Jeong, Sang-Seom;Jung, Hyung-Suh;Whittle, Andrew;Kim, Do-Hyun
    • Journal of the Korean Geotechnical Society
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    • v.37 no.5
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    • pp.5-17
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    • 2021
  • In this study, the shear behavior between pile-sandy soil interface was quantified based on series of rigorous ring shear test results. Ring shearing test was carried out to observe the shear behavior prior to failure and behavior at residual state between most commonly used pile materials - steel and concrete - and Jumunjin sand. The test was set to clarify the shear behavior under various confinement conditions and soil densities. The test results were converted in to representative friction angles for various test materials. Additional numerical analysis was executed to validate the accuracy of the test results. Based on the test results and the numerical validation, it was found that due to the dilative and contractive nature of sand, its interface behavior can be categorized in to two different types : soils with higher densities tend to show peak shear stress and moves on to residual state, while on the other hand, soils with lower densities tend to show bilinear load-transfer curves along the interface. However, the relative density and the confining stress was found to affect the friction angle only in the small train range, and converges as it progresses to large deformation. This study established a large deformation analysis method which can successfully simulate and predict the large deformation behavior such as ring shear tests. Moreover, the friction angle derived from the ring shear test result and verified by numerical analysis can be applied to numerical analysis and actual design of various pile foundations.

The Non Newtonian Flow Mechanism and Rheological Properties of Polyurethane Melts (용융 폴리우레탄의 비 뉴톤 유동 메카니즘과 유변학적인 성질)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.44 no.4
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    • pp.423-428
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    • 2009
  • The non-Newtonian flow curves of polyurethane melts were obtained by using a Physica cone-plate rheometer at various temperatures. The rheological parameters were obtained by applying non-Newtonian flow equation to the flow curves for polyurethane samples. When the polyurethane samples are under increasing-decreasing shear rate modes, the hysteresis loop and thixotropic behavior were shown. Polyurethane melts behave as strong gels when they are subjected to shear flow, but when the applied stress surpasses the yield stress, they exhibit non-linear viscoelasticity. Upon decreasing shear rate, its shear stress remains smaller than the values measured in the increasing shear rate mode, because of broken of its structure.

Reproduction of Cyclic Triaxial Behavior of Unsaturated Soil using Element Simulation (요소 시뮬레이션에 의한 불포화토의 반복삼축거동 재현)

  • Lee, Chungwon
    • Journal of the Korean GEO-environmental Society
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    • v.16 no.10
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    • pp.5-14
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    • 2015
  • Suction affects the unsaturated soil as the negative pore pressure, and leads to increases of the yield stress and the plastic shear stiffness of the soil skeleton due to the growth in interparticle stress. Hence, in this study, in order to account for these effects of suction under the dynamic loading condition such as the earthquake, the element simulation of the cyclic triaxial test using induced stress-strain relation based on cyclic elasto-plastic constitutive model extended for unsaturated soil considering the $1^{st}$ and the $2^{nd}$ yield functions was conducted. Through the stress path, stress-strain relation and relation between volumetric strain and axial strain, it was seen in all the cases that the simulation results demonstrated a good agreement with the experimental results. It is expected that the results of this study possibly contribute to the accuracy improvement on the prediction of unsaturated soil behavior under the dynamic loading condition.

Shear Behavior Prediction of Reinforced Concrete Columns Using Transformation Angle Truss Model (변환각 트러스 모델에 의한 철근콘크리트 기둥의 전단거동 예측)

  • Kim Sang-Woo;Chai Hyee-Dae;Lee Jung-Yoon;Lee Bum-Sik
    • Journal of the Korea Concrete Institute
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    • v.17 no.3 s.87
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    • pp.435-444
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    • 2005
  • This paper predicted the shear behavior of reinforced concrete columns using Transformation Angle Truss Model (TATM) considered the effects of bending moment and axial force. Nine columns with various shear span- to-depth ratios and axial force ratios were tested to verify the theoretical results obtained from TATM. Fine linear displacement transducers (LVDT) were attached to a side of the column near the shear critical region to measure the curvature, the longitudinal and transverse axial deformations, and the shear deformation of the column. The test was terminated when the value of the applied load dropped to about $85\%$ of the maximum-recorded load in the post-peak descending branch. All the columns were failed in shear before yielding of the flexural steel. The shear strength and the stiffness of the columns increased, as the axial force increased and the shear span-to-depth ratio decreased. Shear stress-shear strain and shear stress-strain of shear reinforcement curves obtained from TATM were agreed well with the test results in comparison to other truss models (MCFT, RA-STM, and FA-STM).

Effects of Grain Size Distribution on the Shear Strength and Rheological Properties of Debris Flow Using Direct Shear Apparatus (직접전단장비를 이용한 토석류의 전단강도 및 유변학적 특성에 대한 입도분포의 영향 연구)

  • Park, Geun-Woo;Hong, Won-Taek;Hong, Young-Ho;Jeong, Sueng-Won;Lee, Jong-Sub
    • Journal of the Korean Geotechnical Society
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    • v.33 no.12
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    • pp.7-20
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    • 2017
  • In this study, effects of grain size distribution on the shear strength and rheological properties are investigated for coarse- and fine-grained soils by using direct shear apparatus. Shear strengths are estimated for fine-grained soils with the maximum particle size of 0.075 mm and coarse-grained soils with the maximum particle size of 0.425 mm and fine contents of 17% prepared at dry and liquid limit states. The direct shear tests are conducted under the relatively slow shear velocity, which corresponds to the reactivated landslide or debris flow after collapse according to the landslide classification. In addition, for the evaluation of rheological properties, residual shear strengths for both fine- and coarsegrained soils prepared under liquid limit states are obtained by multiple reversal shear tests under three shear velocities. From the relationship between residual shear strengths and shear rates, Bingham plastic viscosity and yield stress are estimated. The direct shear tests show that cohesions of fine-grained soil are greater than those of coarse-grained soil at both dry and liquid limit states. However, internal friction angles of fine-grained soil are smaller than those of coarse-grained soil. In case of rheological parameters, the plastic viscosity and yield stress of fine-grained soils are greater than those of coarse-grained soils. This study may be effectively used for the prediction of the reactivated landslide or debris flow after collapse.