• Title/Summary/Keyword: 체적변형률

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분자동역학을 이용한 다공성 물질 건조공정 멀티스케일 시뮬레이션(1부 : 균질화법 해석)

  • 금영탁;오진원;백성민
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.05a
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    • pp.67-67
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    • 2004
  • 다공성 물질을 건조하거나 습한 환경에 노출시키면 열과 수분이 외부로 전달된다. 열 및 수분 전달로 인한 은도 및 습도의 변화는 물질 체적을 변화시켜 습열 응력을 유발시킨다 즉 다공성 제품의 품질은 외양뿐만 아니라 건조 공정 시의 온도, 수분함유량, 응력, 변형률 등의 공정변수에 크게 영향을 받는다. 최근까지도 다공성 물질의 생산 공정은 다수의 공정변수를 갖는 복합공정이기 때문에 이들의 영향을 정량적으로 평가하는 것은 매우 까다로워 현장 경험에 기초한 기술자의 노하우에 의존해 왔다.(중략)

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An Experimental Study on Uniaxial Compressive Behavior of RC Circular Columns Laterally Confined with Prestressing Aramid Fiber Strap (아라미드 스트랩으로 프리스트레싱 횡구속된 RC 원형기둥의 일축압축거동에 관한 실험적 연구)

  • Han, Sang-Hoon;Hong, Ki-Nam;Lee, Jae-Bum
    • Journal of the Korea Concrete Institute
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    • v.21 no.2
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    • pp.159-168
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    • 2009
  • In this study, strength, stiffness and confinement effect with stress-strain and stress-volumetric strain curves for improved uniaxial compressive behavior of RC circular columns laterally confined with prestressing aramid fiber strap were experimentally investigated. The test variables were the specimens with or without axial reinforcing bar and the number and spacing of strap, prestressing level, the types of reinforcing fiber (CFS, GFS). As a result, the failure type of the columns was very stable and strength increase rate was about 73% comparison with the general RC columns. Moreover, the strain increase rate is very small and the axial displacement confinement effect was very effective compared with existry methods (CFS, GFS), the initial and final lateral confinement effect was excellent.

Characteristics of Pore Pressure and Volume Change During Undrained lending of Unsaturated Compacted Granite Soil (비배수전단시 불포화 다짐화강토의 간극압과 체적변형특성)

  • 김찬기;김태형;이종천
    • Journal of the Korean Geotechnical Society
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    • v.19 no.4
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    • pp.15-21
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    • 2003
  • A series of triaxial compression tests were performed on samples of compacted granite soil in a modified triaxial cell that allowed separate control of pore air pressure ($U_a$) and pore water pressure ($U_w$) in order to examine the characteristics of pore pressure, volume change and stress-strain behavior during undrained loading conditions. Triaxial samples of unsaturated and saturated compacted granite soil, 50mm in diameter and 100mm in height, were prepared by compaction in a mould. These samples were tested at 3 different suction values (0.5, 1.0, 2.0 kgf/cm$^2$) for unsaturated compacted granite soil and at 3 different confining stresses (1.0, 2.0, 4.0 kgf/cm$^2$). Results showed that only effective cohesion increased with little variation of friction angle, according to matric suction.

Three dimensional accuracy analysis of dental stone casts fabricated using irreversible hydrocolloid impressions (알지네이트 인상체에서 제작된 치과용 석고 모형의 정확도에 대한 삼차원 디지털 분석)

  • Joo, Young-Hun;Lee, Jin-Han
    • Journal of Dental Rehabilitation and Applied Science
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    • v.31 no.4
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    • pp.316-328
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    • 2015
  • Purpose: The objects of this study was to evaluate the accuracy of the dental stone casts made from alginate impressions according to storage condition and stone pouring time. Materials and Methods: Each of upper and lower impressions of dental model was taken. The dental stone models were made immediately, 10, 30, 60, 180, 360 minutes after the impressions were taken at each storage condition. 3D models were constructed by scanning the stone model using 3D laser scanner. With Reference points, positioned on digital models, linear measurements of the dimensional change were compared by 3D metrology software, 3D average models were made and superimposition to identify the specific site of dimensional change and to measure surface deviation (mm). Results: Dental stone models which were made immediately after taking the impression showed the smallest linear dimensional change. As the stone pouring time was prolonged, the linear dimensional change was increased. More than 180 minutes after impression taking, linear dimensional change and surface distortion increased in the posterior molar region, regardless of the storage condition. Conclusion: For the optimum accuracy of the dental stone casts, alginate impression should be poured as soon as possible. If there were a need for storing, a humidor with 100% relative humidity must be used and be stored less than 180 minutes to fabricate the accurate dental model.

A Characteristics of Shear Strength and Deformation of Decomposed Granite Soil (화강토의 전단강도 및 변형특성)

  • 박병기;이강일
    • Geotechnical Engineering
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    • v.13 no.4
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    • pp.177-198
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    • 1997
  • Since decomposed granite soil shows various characteristics of shear behavior dependent on initial conditions such as weathering degree and grain breakage, it is nacessary to invert ligate stress -strain relationship and changes of shear characteristics for different initial conditions. Associated with abovefnentioned view, direct shear tests, and triaxial compression tutsts(Ef, CD) were carried out in this study for undisturbed and disturbed compacted weathered granite samples obtained from 4 construction work sites with the various weathering degree and components of parent rocks. The deformation behavior of undisturbed samples under small confining stress shows hardening to softening, which is similar to that of over nsolidated clay whereas disturbed weathered granite soils do hardeningfonstant regardless of weathering degree, which is also similar to sedimentary clay. Conventional direct shear-tests for undisturbed samples show a tendency to overestimate cohesion. It is possidle to approximate stress ratio(q/p') and volumetric increment ratio(dv/ds) in the triaxital compression tests by an equation, ($dv/d\varepsilon,=\alpha(M-\eta))$ irrespective of moisture content, weathering degree and disturbance.

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The Stress -Strain Behavior of Asan Marine Soil (아산만 해성토의 응력 -변형률 거동)

  • Hong, Chang-Su;Jeong, Sang-Seom;Kim, Su-Il
    • Geotechnical Engineering
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    • v.12 no.5
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    • pp.17-26
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    • 1996
  • The undrained behavior of Asan marine soil was investigated by using an automated triaxial testing device. The stress-strain behavior at the preand postfailure state of marine soil under undrained compression and eatension conditions was compared with the behavior of pure silt, pure clay and the overall behavior of Asan marine soil was predicted with the modified Camflay model and the bounding surface model. The marine soil sampled in Asan bay area was clayey silts with 70oA silt-30% clay content and the testing samples were prepared in both undisturbed and remolded conditions. All samples are normally consolidated with 400 kPa of effective mean confining pressure and each sample is unloaded to 200, 100, 67 kPa, respectively. And then the shear test was performed with different confining pressure. According to experimental results, there exists an unique failure line whose slope is lower than silt's and higher than clay's. It is identified that the undrained shear strength of normally consolidated samples increases after crossing the phase transformation line because of volume dilation tendency which is not seen in clay. Overconsolidated samples show different soil behavior compared with pure silt due to its tendency of change in volume. It is also found that the overall behavior of Asan marine soil cannot be predicted precisely with the modified Cam-clay model and the bounding surface model.

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Numerical Analysis of Anisotropic Soil Deformation by the Nonlinear Anisotropic Model (흙의 변형 거동 예측을 위한 비선형 이방성 모델의 개발과 적용)

  • 정충기;정영훈;윤충구
    • Journal of the Korean Geotechnical Society
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    • v.18 no.5
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    • pp.237-249
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    • 2002
  • Nonlinearity and anisotropy of soil should be considered for the exact prediction of deformation before the failure state. In this study, a new constitutive model is developed in which the nonlinearity of soil is formulated by Ramberg-Osgood equation and the soil anisotropy is implemented by the cross-anisotropic elasticity. Nonlinear anisotropic model and other models for comparison are used to analyze the simple boundary value problems and the circular footing problem. In the results, the anisotropic ratio of elastic modulus is a key value for the bulk modulus of soil, the coeffcient of earth pressure at rest, and the slope of effective stress paths. Furthermore, it is found that the nonlinearity of soil considering the in-situ stresses has the great influence on the magnitude of settlements.

Aseismic analysis for large underground structure (대형 지하구조물의 내진해석)

  • Choi, Seung-Ho;Pam, Inn-Joon;Kim, Sang-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.2
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    • pp.163-174
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    • 2009
  • The large underground structure under earthquake is affected more by soil dynamic characteristic and volume of structure than by structural dynamic characteristic itself. Therefore, it is the purpose of research that the aseismic analysis for caverns including various aseismic analysis factors (rock quality-Q value, soil dynamic characteristic, shape ratio $&$ volume, underground structural dynamic characteristic, and aseismic level) are applied by using the numerical analysis program (SAUS; seismic analysis of underground structures). The result of research is stated that maximum strain, maximum moment, and maximum shear are not sensitive with respect to shape ratio. However those values are sensitive with respect to Q value, volume of underground structure and aseismic level. Based on the results of this research, the assessment for the influence factors of aseismic analysis for large underground structure could be possible.

Sensitivity of Parameters for Elasto-plastic Constitutive Model (탄.소성 구성 모델의 초질매개변수 예민성)

  • Jeong, Jin-Seop;Kim, Chan-Gi;Lee, Mun-Su
    • Geotechnical Engineering
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    • v.8 no.2
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    • pp.81-96
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    • 1992
  • This paper dealt with the influence of experimental error generated inevitably during performing experiments on the granular soil behaviour analysis selecting Lade's Single Work-Hardening constitutive model. Several isotropic compression-expansion tests and a series of drained conventional triaxial tests with various confining pressures for Baekma river sands were performed and the values of parameters for the above model were determined using computer program developed for this study based on regression analysis. By finding the range of the upper and lower bound for deviator stress and volumetric strain versus axial strain dependant on the increase and decrease of the standard deviation from mean value of parameters, sensitivities of all the parameters were examined. Practical use of program to determine the parameters and capability to predict the behaviour of granular soil by Lade's Single Work -Hardening model verified.

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Generalized Lateral Load-Displacement Relationship of Reinforced Concrete Shear Walls (철근콘크리트 전단벽의 횡하중-횡변위 관계의 일반화)

  • Mun, Ju-Hyun;Yang, Keun-Hyeok
    • Journal of the Korea Concrete Institute
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    • v.26 no.2
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    • pp.159-169
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    • 2014
  • This study generalizes the lateral load-displacement relationship of reinforced concrete shear walls from the section analysis for moment-curvature response to straightforwardly evaluate the flexural capacity and ductility of such members. Moment and curvature at different selected points including the first flexural crack, yielding of tensile reinforcing bar, maximum strength, 80% of the maximum strength at descending branch, and fracture of tensile reinforcing bar are calculated based on the strain compatibility and equilibrium of internal forces. The strain at extreme compressive fiber to determine the curvature at the descending branch is formulated as a function of reduction factor of maximum stress of concrete and volumetric index of lateral reinforcement using the stress-strain model of confined concrete proposed by Razvi and Saatcioglu. The moment prediction models are simply formulated as a function of tensile reinforcement index, vertical reinforcement index, and axial load index from an extensive parametric study. Lateral displacement is calculated by using the moment area method of idealized curvature distribution along the wall height. The generalized lateral load-displacement relationship is in good agreement with test result, even at the descending branch after ultimate strength of shear walls.