• Journal of the Korean Geotechnical Society
• /
• v.24 no.7
• /
• pp.25-36
• /
• 2008

The plane strain test can reproduce the real field condition and failure behavior precisely over other laboratory shear tests. Accordingly, this test has been utilized to investigate the shearing behaviors associated with overall failure behavior and local deformation of soils. However, most plane strain tests have been carried out with restrained end plates due to difficulties in manufacturing the equipment and also performing it. This restraint induces different results with real field because of shear stress on end plates. In this study, plane strain tests with/without bottom plate restraint were performed on Jumunjin-sand. The measurement of overall and local deformation was accomplished by digital image correlation technique as well as external LVDT. By applying digital image correlation method using two consecutive images captured through the transparent wall, local deformation behavior of various parts inside the specimen was estimated. And the formation and development of shear band caused by the restrained effect of end plate and the deformation mechanism of sand under plane strain condition were examined.

• Journal of the Korea Concrete Institute
• /
• v.14 no.6
• /
• pp.910-921
• /
• 2002

For the prediction of shear behavior of reinforced concrete beams, this paper proposed Transformation Angle Truss Model (TATM) considered bending moment effect. Shear stress-strain relationship obtained from the TATM was agreed well with test results conducted by this study Further, shear strength obtained from the TATM was compared to the experimentally observed results of 170 reinforced concrete beams which had various shear span ratios shapes of support and shapes of cross section. The shear strength of reinforced concrete beams obtained from test was better predicted by the TATM with 0.96 in average and 11.9％ in coefficient of variation than by other truss models. And the ratio of experimental results to theoretical results obtained from the TATM was almost constant regardless of the η and a/d.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.4
• /
• pp.51-65
• /
• 2011

Shear banding, the localization of deformation into thin zones, has a quite practical relevance, as stability and deformation characteristics of earth structures are controlled by the soil behavior within the shear band. In this study, for understanding occurrence and developed pattern of shear band, plane strain compression tests were performed on three soils with different particle-size distribution under various conditions. Digital images were captured during the experiments; then, deformation of a specimen was evaluated by digital image analysis technique. The characteristics of a shear band were evaluated from the state shortly after post-peak occurrence to critical state. Additionally, the statistical procedure was developed to determine the reasonable thickness of a shear band.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.5
• /
• pp.67-75
• /
• 2014

In this paper, isotropically consolidated drained triaxial compression test device installed with bender elements is used to measure stress, stain, and shear wave velocity, from which the characteristics of shear strength and Poisson'ratio are investigated. The results show that there is a unique relationship between maximum shear modulus determined from shear wave velocity and effective vertical stress at failure, which is defined as the sum of vertical and radial stresses at failure. The correlation is very useful since it is possible to predict the shear strength and internal friction angle from shear wave velocity. In addition, Poisson's ratio is determined from measured axial and volumetric strains. It is demonstrated that the range of measured Poisson's ratio is between 0.15 and 0.6, and increases with the axial strain. The ratios at axial strains smaller than 0.2% corresponds to the range recommended in design codes, which are approximately from 0.3~0.35. However, at axial strains exceeding 1%, the measured ratios are between 0.5 and 0.6. It is therefore shown that use of ratios commonly used in practice will result in pronounced underestimation at large strains.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.6
• /
• pp.335-342
• /
• 2003

In order to analyze the deformational behavior accurately, the in-situ testing technique which provides the reliable deformational characteristics at whole strain ranges, needs to be developed. The pressuremeter is a unique method for assessing directly the in-situ shear modulus of soils with strain amplitude. This paper introduces a new alternative, the cavity strain measuring system in pressuremeter designed for whole strain ranges of $10^{-5}$%∼20%. Not only in the synthetic calibration chamber but also in the field, the pressuremeter tests were performed to determine the compliance of the new developed pressuremeter system. The variation in shear modulus with strain amplitude above $5\times 10^{-2}$% was reliably determined by the developed pressuremeter. It is concluded that the major cause of error in small cavity strain measuring is not from the cavity strain measuring system but from the friction between measuring arm and membrane during unloading-reloading loops.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.12 no.2
• /
• pp.105-116
• /
• 2010

The estimation of surface settlement, ground behavior and tunnel displacement are the main factors in urban tunnel design with shallow depth and unconsolidated soil. On deformation analysis of shallow tunnel, it is important to identify possible deformation mechanism of shear bands developing from tunnel shoulder to the ground surface. This paper investigated the effects of key design parameter affecting deformation behavior by numerical analysis using nonlinear model incorporating the reduction of shear stiffness and strength parameters with the increment of the maximum shear strain after the initiation of plastic yielding. Numerical parametric studies are carried out to consider the reduction of shear stiffness and strength parameters, horizontal stress ratio, cohesion and shotcrete thickness.

• Journal of the Korea Concrete Institute
• /
• v.19 no.6
• /
• pp.685-692
• /
• 2007

When the shear force governs the response of an RC element, as in the case of a low-rise shear wall, the effect of shear on the element's response is thought to be responsible for the 'pinching effect' in the hysteretic loops. However, it was recently shown that this undesirable pinching effect can be eliminated in the hysteretic load-deformation curves of a shear-dominant element if the steel grid orientation is properly aligned in the direction of the applied principal stresses. In this paper, the presence and absence of the pinching mechanism in the hysteretic loops of the shear stress-strain curves of RC elements was explained rationally using a compatibility aided truss model. The analytical results indicate that the pinching effect of the RC elements is strongly related to the direction of the steel arrangement. The area of the energy dissertation does not increase proportionally to the difference between the direction of the principal compressive stress and the direction of the steel arrangement.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.3 s.49
• /
• pp.113-123
• /
• 2006

An experimental investigation on the behavior of reinforced concrete coupling beams is presented. The test variables are the span-to-depth ratio, the ratio of flexural reinforcements and the ratio of shear rebars. The distribution of arch action and truss action which compose the mechanism of shear resistance is discussed. The increase of plastic deformation after yielding transforms the shear transfer by arch action into by truss action. This study proposes the deformation model for reinforced concrete coupling beams considering the bond slip of flexural reinforcement. The strain distribution model of shear reinforcements and flexural reinforcements based on test results is presented. The yielding of flexural reinforcements determines yielding states and the ultimate states of reinforced concrete coupling beam are defined as the ultimate compressive strain of struts and the degradation of compressive strength due to principal tensile strain of struts. The flexural-shear failure mechanism determines the ultimate state of RC coupling beams. It is expected that this model can be applied to displacement-based design methods.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.3
• /
• pp.506-513
• /
• 1992

본 연구에서는 복합재 구조물에 대하여 유한요소해석법에 현상학적 모델인 전 단지연해석을 도입하여 강성저하와 모재파손을 예측하고 변형률을 매개변수로 한 Wei- bull 함수를 섬유파손해석에 도입하여 초기파손후의 거동을 묘사하고자 한다. 그리 고 면내전단하중이 작용하는 경우에 대해 전단지연해석을 수행할 수 있도록 모델링을 확장했다. 모재균열의 존재로 인한 단층의 강성변화는 실험으로 측정이 불가능하므 로 유한요소해석을 수행하여 비교하였다. 이 모델로부터 전단강성의 저하를 평가하 는 방법을 사용하였으며, 모재파손의 밀도 예측도 평균변형률 개념으로 전단효과를 고 려할 수 있도록 수정하였다. 그리고 초기파손후의 거동을 점진적으로 해석하기 위해 비선형 유한요소프그램을 작성하고, 상기의 모델을 도입하여 초기파손후의 거동을 보 다 정확히 묘사할 수 있는 방법을 제시하고 예로서 평시편에 대해 해석하고 실험치 및 타방법의 결과와 비교하였다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.12 no.4
• /
• pp.295-306
• /
• 2010

Contrary to an intact rock, the jointed rock mass shows strain-dependent deformation characteristics (elastic modulus and damping ratio). The maximum elastic modulus of a rock mass can be obtained from an elastic wave-based exploration in a small strain level and applied to seismic analyses. However, the assessment and application of the non-linear characteristics of rock masses in a small to medium strain level ($10^{-4}{\sim}0.5%$) have not been carried out yet. A non-linear dynamic analysis module is newly developed for FLAC3D to simulate strain-dependent shear modulus degradation and damping ratio amplification characteristics. The developed module is verified by analyzing the change of the Ricker wave propagation. Strain-dependent non-linear characteristics are obtained from disks of cored samples using a rock mass dynamic testing apparatus which can evaluate wave propagation characteristics in a jointed rock column. Using the experimental results and the developed non-linear dynamic module, seismic analyses are performed for the intersection of a shaft and an inclined tunnel. The numerical results show that vertical and horizontal displacements of non-linear analyses are larger than those of linear analyses. Also, non-linear analyses induce bigger bending compressive stresses acting on the lining. The bending compressive stress concentrates at the intersection part. The fundamental understanding of a strain-dependent jointed rock mass behavior is achieved in this study and the analytical procedure suggested can be effectively applied to field designs and analyses.