• 한국방재학회 논문집
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• 제8권2호
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• pp.97-103
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• 2008

Determination of stress-strain relationship in torsional tests is complicated due to nonuniform stress-strain variation occurring linearly with the radius in a soil specimen in torsion. The equivalent radius approach is adequate when calculating strain at low to intermediate strains, however, the approach is less accurate when performing the test at higher strain levels. The modified equivalent radius approach was developed to account for the problem more precisely. This approach was extended to generate the plots of equivalent radius ratio versus strain using modified hyperbolic and Ramberg-Osgood models. Results showed the effects of soil nonlinearity on the equivalent radius ratio curves were observed. Curve fitting was also performed to find the stress-strain relationship by fitting the theoretical torque-rotation relationship to measured torque-rotation relationship.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.361-364
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• 2004

This paper predicts the shear stress-strain relationship of reinforced concrete columns using Transformation Angle Truss Model (TATM) considered bending moment and axial force effects. Nine columns with various shear span-to-depth ratios and axial force ratios were tested to verify the theoretical results obtained from TATM. Shear stress-strain relationship obtained from TATM was agreed well with test results conducted by bis study than other truss models.

• Geomechanics and Engineering
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• 제17권2호
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• pp.145-156
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• 2019

Since behaviors of loose, dense, silty sands vary under seismic loading, understanding the liquefaction mechanism of sandy soils continues to be an important challenges of geotechnical earthquake engineering. In this study, 36 deformation controlled cyclic simple shear tests were performed and the liquefaction potential of the sands was investigated using three different relative densities (40, 55, 70%), four different effective stresses (25, 50, 100, 150 kPa) and three different shear strain amplitudes (2, 3.5, 5%) by using energy based approach. Experiments revealed the relationship between per unit volume dissipated energy with effective stress, relative density and shear strain. The dissipate energy per unit volume was much less affected by shear strain than effective stress and relative density. In other words, the dissipated energy is strongly dependent on relative density and effective stress. These results show that the dissipated energy per unit volume is very useful and may contain the non-uniform loading conditions of the earthquake spectrum. When multiple regression analysis is performed on experiment results, a relationship is proposed that gives liquefaction energy of sandy soils depending on relative density and effective stress parameters.

• Geomechanics and Engineering
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• 제1권4호
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• pp.263-274
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• 2009

The modified Cam clay (MCC) model is used to study the response of virgin compressed clay in undrained compression. The MCC deviatoric stress-strain relationship is obtained in closed form. Elastic and plastic deviatoric strains are taken into account in the analysis. For the determination of the elastic strain components, both a variable shear modulus and constant shear modulus are considered. Constitutive relationships are applied to the well-known London and Weald clays sheared in undrained compression.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1039-1046
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• 2005

After clay particles have been sediment isotropically, the clay deposits have been consolidated under $K_0$-stress system. Therefore, in order to predict the behavior in-situ of normally consolidated clays, the laboratory test should be enforced under $K_0$-stress system and should obtain the characteristics of normally consolidated clays. And relationship of stress-strain on clay is effected on not only method of consolidation but also characteristic of visco-plastic behavior. Saturated clay is effected more this trend. So, rate of strain is considered to understand exact stress-strain relationship. In this study, the series of undrained triaxial compression tests were preformed on remolded specimens which was made by slurry of clay, consolidated under $K_0$-stress systems. And the undrained triaxial compression test were preformed to examine behavior of stress-strain relationship due to rate of shear strain relationship due to rate of shear strain.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.139-146
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• 2001

Undrained triaxial tests were peformed for a weathered soil, which includes local measurement using LVDT The behavior from small In large strain conditions could be evaluated consistently through a triaxial test, The stress-strain relationship of undisturbed samples were compared with the disturbed and the shear moduli in the small strain level had the almost same values. Especially the shear moduli were mostly affected by the initial condition of water contents. An anisotropic hardening model based on the total stress concept could predict the stress-strain relationship accurately, which makes it possible to analyze the geotechnical problem reasonably for the weathered soil.

• 한국농공학회지
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• 제30권4호
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• pp.134-153
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• 1988

This paper was carried out to investigate the existence of a unique stress- strain behavior by obtaining some factors influencing the time dependent stress- strain behavior of clay. The results obtained from this study were summarized as follows ; 1. The relationship between stress ratro and strain in normally consolidated clay was in- dependent on pre-shear consolidation pressure. Therefore, shear strain could be expressed as a function with stress ratio. 2. The constitutive equation of shear strain on Modified Carn Clay Model coincided better with the observed value than Cam Clay Model. 3. The relationships between deviator stress and shear strain, between pore water pressure and shear strain were unified by the mean equivalent pressure. 4. The shear strain contour in norrnally consolidated clay was increased linearly through origin, but that in overconsolidated clay was not in accordance with the result of the former. 5. Because the effective stress path of normally consolidated clay was unified by the mean equivalent pressure, state boundary surface in (e,p,q) space was transformed into two dimensional surface. But it was considered to be suitable that the unified stress- strain in overconsolidated clay be expressed by a function with overconsolidation ratio. 6. The deviator for constant strain was increased linearly with increment of strain rate ($\varepsilon$) on semi-log scale, but pore water pressure was decreased. 7. The behavior of stress relaxation was transformed from linear to curvilinear with inc - rement of strain rate before stress relaxation test, and pore water pressure was increased in total range. 8. The strain of creep was increased linearly with increment of time on semi-log scale. The greater the strain rate before creep test became, the greater the increment of strain of creep became. And the pore water pressure during creep test was increased generally with increment of time on semi-log scale.

• Geomechanics and Engineering
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• 제13권5호
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• pp.743-756
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• 2017

Laboratory investigation reveals that rockfills exhibit significant stress-path-dependent behavior during shearing, therefore realistic prediction of deformation of rockfill structures requires suitable constitutive models to properly reproduce such behavior. This paper evaluates the capability of a strain hardening model proposed by the authors, by comparing simulation results with large-scale triaxial stress-path test results. Despite of its simplicity, the model can simulate essential aspects of the shear behavior of rockfills, including the non-linear stress-strain relationship, the stress-dependence of the stiffness, the non-linear strength behavior, and the shearing contraction and dilatancy. More importantly, the model is shown to predict the markedly different stress-strain and volumetric behavior along various loading paths with fair accuracy. All parameters required for the model can be derived entirely from the results of conventional large triaxial tests with constant confining pressures.

• 대한토목학회논문집
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• 제35권1호
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• pp.101-110
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• 2015

최근 Hsu는 전단시험장치를 이용해 순수전단이 작용하는 9개 RC패널요소의 전단시험을 수행하였다(ACI 1997). 최신 트러스모델(수정압축장이론, 회전각연성트러스모델)은 평형조건과 적합조건 그리고 2축 상태에서 RC 막판넬의 연성 응력-변형률 관계를 이용하여 2중 루프의 시행착오방법으로 복잡한 비선형해석을 수행하고 있다. 본 연구는 스트럿과 타이의 파괴기준에 기반한 개선된 모어변형적합방법을 사용해 효율적인 알고리즘을 제안하였고, 이 알고리즘을 이용하여 Hsu가 실험한 전단이력 해석을 빠른 수렴속도로 개선한 것이다. 해석결과에 의하면 전단변형률 증폭상태의 전단변형에너지는 주압축 응력-변형률에 크게 지배받는 것으로 나타났다.

• 한국지반환경공학회 논문집
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• 제11권11호
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• pp.55-62
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• 2010

액상화에 의해 발생되는 피해의 상당 부분은 반복전단과정에서 발생한 과잉간극수압이 소산되면서 지표에 나타나는 침하에서 유발된다. 그러나 지반은 매우 복잡한 구조로 되어 있기 때문에 침하는 균등하게 발생하지 않으며 대부분 부등 침하의 형태로 발생되게 된다. 일반적으로는 이러한 잔류전단변형률이 없는 상태에서 재압밀을 수행하지만 현실적으로는 잔류전단변형이 남아있는 것이 자연스러운 현상이라는 인식과 함께 다양한 다이레이턴시 특성하에서 발생되는 액상화 후 재압밀에 대한 고찰이 거의 이루어지지 않았다는 점에 주목하여 본 연구에서는 잔류전단변형률이 액상화 후 재압밀과정에 미치는 영향을 검토하였다. 이를 위하여 변형률 제어에 기반을 둔 시험장치와 간극수의 배수를 정밀 제어할 수 있는 체적변형률 제어장치를 이용하여 세립분을 포함하고 있지 않은 표준사와 세립분을 포함한 풍화토에 대한 일련의 삼축압축시험을 실시하였고 그 결과를 고찰하였다. 결과 표준사의 경우 에는 상대적으로 잔류전단변형률이 액상화 후 체적압축특성에 미치는 영향이 작았으나 풍화토의 경우에는 유효응력-체적변형률 관계곡선이 잔류전단변형률이 클수록 하방에 위치하였으며 곡선의 형상에도 영향을 미치고 있었고 대체적으로 응력 수준이 낮은 배수 초기에 체적변형률이 급증하며 유효응력 증가에도 거의 체적변형은 일어나지 않고 있다. 액상화에 의한 침투유동파괴가 낮은 응력 수준에서 발생된다는 점을 고려하면 이러한 관계 곡선의 형상은 매우 중요한 의미를 갖는다.