• Journal of the Korea Academia-Industrial cooperation Society
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• 제16권10호
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• pp.6846-6851
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• 2015

In this study, equation of calculating vertical stress increment developing in underneath of the embankment due to the extension of embankment width was derived through the use of theory of elasticity. Concept of the origin of plane was adopted to simplify derivation procedure for obtaining the equation. Comparing the results of the equation for calculating vertical stress increment with those of the numerical analyses, differences in the magnitudes of vertical stress increments decrease as the depths below embankment increase. Comparing the vertical stress increments with horizontal distances which correspond to certain depth, vertical stress increments obtained from the derived equation were slightly greater than those of numerical analyses.

• Geotechnical Engineering
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• 제1권1호
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• pp.73-84
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• 1985

This Paper aims at investigating the distribution of stresses and the displacement of soft foundation layer subject to embankment load by the finite elements method (FEM). The stresses include the volumetric stress, the Pore water Pressure, the vertical stress. The horizontal stress and the shear stress. The Christian-Boehmer's method was selected as technique for FEM and the general elasticity model and modified Cam-clay model as the governing equations under Plain-strain condition depending on drained and undrained conditions. The results obtained are as follows: 1. The volumetric stress is almost consistent with the pore water pressure. This means that the total stress is the same value with the pore water pressure under the undrined condition 2. The vertical stress appears in the same value regardless of the drained or undrained condition and the model of the constitutive equations. 3. The horizontal stress has almost same value with the drain condition model. 4. depending on the constitutive model. The shear stress is affected by both the drain condition and the constitute model. The resulted value by the modified Cam-clay model has the largest. 5. The direction of the displacement vector turns outward near the tip of load during the increasing load. 6. The magnitude of displacement due to the modified Cam.clay model is as twice large as that due to elastic model.

• Journal of the Korea Concrete Institute
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• 제16권5호
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• pp.677-686
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• 2004

This study deals with literature review, developing a predicting equation for the ultimate stress of internal and external prestressing steel, and an experimental test with the parameters affecting the ultimate stress of prestressing steel in prestressed concrete beams strengthened by external prestressing tendons. The proposed predicting equation takes rationally the effect of internal and external prestressing steels into consideration as a function of prestressing steel depth to neutral depth ratio. In the experimental study, prestressed concrete beams strengthened using external steel tendons are tested with the test parameters having a large effect on the ultimate stress of internal and external prestressing steel. The test parameters include internal and external prestressing steel reinforcement ratio and span to depth ratio. The test results are analyzed to confirm the rationality and applicability of the proposed equation for predicting the ultimate stress of internal and external prestressing steel. This research shows that the results obtained by the proposed equation for predicting the ultimate stress agreed very well with the test results.

• Tunnel and Underground Space
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• 제22권1호
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• pp.12-21
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• 2012

Although the Mohr-Coulomb and Hoek-Brown failure criteria have been adopted widely in rock mechanics, they neglect the ${\sigma}_2$ effect. The result of true triaxial tests on rock samples, however, reveals that the ${\sigma}_2$ effect on strength of rocks is considerable, so that rock failure criteria taking into account the influence of ${\sigma}_2$ are necessary for the precise stability evaluation of rock structures. In this study, a new nonlinear 3-D failure criterion has been suggested by combining the Hoek-Brown criterion with the smooth octahedral shape function taken from Jiang & Pietruszczak (1988). The performance of the new criterion was assessed by comparing the strength predictions from both the suggested criterion and the corresponding linear 3-D criterion. The resulting fit of the new criterion to the true triaxial test data for six rock types taken from the literature shows that the criterion fits the experimental data very well. Furthermore, for the data sets having data taken in the low ${\sigma}_3$ range, the nonlinear failure criterion works better than the linear criterion.

• Journal of the KSME
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• 제29권3호
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• pp.231-243
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• 1989

복합재료의 탄성 문제를 정리하면 다음과 같다. 복합재료와 등방성 재료의 탄성학적 차이는 재료의 탄성계수에 기인하며 이것은 각각 다른 형태의 응력-변형률관계를 갖게 한다. 한편 응 력-변형률 관계식을 제외한 탄성학의 지배방정식은 재료의 종류에 관계없이 성립한다. 복합적 층판의 Stiffness와 응력 등은 Lamination 이론을 사용하여 구할 수 있다. 판이론은 평형식을 z방향으로 적분한 식, 즉 합력(resultant force)와 모멘트로 나타낸 평형식을 사용하는데 이 때 처짐 방정식을 구하기 위해 합력. 모멘트-곡률. 변형률 관계식을 이용하는데 이 관계식이 복합 재료와 등방성재료가 상이하다. 결과로 복합재료는 커플링 효과를 갖게 되며, 복합적층판을 대 칭으로 쌓으면 이 효과를 상쇄시킬 수 있다. 복합적층 보의 이론은 유효 굽힘 계수를 도입하면 등방체 보 이론을 사용하여 보의 처짐을 해석할 수 있다. 복합적층 보의 경우 굽힘 응력의 최 대치는 등방체와는 달리 보의 표면에서만 일어나지 않고 내부에서도 일어날 수 있다.

• Tunnel and Underground Space
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• 제13권3호
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• pp.169-179
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• 2003

Anisotropic shear strength of rock joints is studied based on the artificially fractured specimens using experimental and analytical methods. Series of direct shear tests are performed to obtain the strength, stiffness and friction angle of joints under various low normal stresses and shearing directions. The results of shear strength and stiffness show anisotropic value according to shearing direction under low normal stress specially less than 2.45 MPa. But, the effect of joint roughness on strength decreases with increasing normal stress. To estimate more effectively the peak shear strength under low normal stress, the modified Barton's equation is suggested.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제31권1호
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• pp.39-46
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• 2018

In this paper, an unbonded post-tensioning anchorage for a single-stranded wire that allows more efficient stress distribution in the post-tensioned anchorage zone was developed by using a finite element analysis using a commercial program. The stress analysis was carried out using a 3D model in the anchorage zone of the concrete member using the developed anchorage. The result of analysis ensured that the developed anchorage reduced the maximum bursting stress in anchorage zone compared to the case of existing anchorage and the location where maximum bursting stress also occurred closer to the anchorage. Bursting force was calculated using AASHTO, modified $M{\ddot{o}}rsch$ and Stone. As a result, it was concluded that an effective reinforcement design of the anchorage zone can be designed by modified $M{\ddot{o}}rsch$.

• Journal of the Korean Geotechnical Society
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• 제15권1호
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• pp.5-13
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• 1999

Maximum stress in pile is developed when it is driven. If the stress is greater than allowable stress of the pile, the pile will be damaged and result in stability problem. Therefore, the stress should be estimated correctly beforehand and overstress should be prevented during pile driving. There are many methods to estimate compressive stresses in concrete piles when they are driven. Nowadays, computer analysis on wave equation offers a satisfactory results. But. under certain circumstances, application of this method is difficult. Then, estimation of the stress utilizing simple formulae might be practical. In this study, relatively reasonable formulae were selected and the stresses which were measured in situ and calculated from the formulae were compared and analysed. The results show that the calculated values from Uto and Huyuki's formula were reasonably accurate and more accurate values were acquired if the values are modified by multiplying the reduction factors according to ground and construction conditions.

• Magazine of the Korea Concrete Institute
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• 제11권1호
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• pp.209-219
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• 1999

This paper describes an experimental study planned to examine the effects of important design variables which were used in the proposed equation by authors. Fourteen beams and slabs were designed with the variables, such as effective prestress, concrete strength, amount of tendons, amount of bonded reinforcements, loading type, and span/depth ratio. Then, deflections and tendon stresses were measured and compared according to the parametric variations of the selected variables. It was found that the tendon stress increment decreases as the level of effective prestress or the amount of unbonded tendons and bonded reinforcements increases. Also, the contributions of concrete strength, and loading type were observed to affect on the tendon stresses. However, the stress increments of unbonded tendon were minimal alt high values of span/depth in contrast with the ACI code.

• The Korean Journal of Rheology
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• 제9권3호
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• pp.124-131
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• 1997

스테인레스 강(SUS 316L) 분말과 왁스계 결합제를 혼합하여 제조한 분말사출재의 유변학적 특성을 낮은 전단율에서 측정하기 위해 동심원반식 점성측정기를 이용하여 실험을 실시하였다. 측정기 벽면에서 발생하는 벽면 슬립(Slip)을 확인하고 벽면 슬립을 보정하기 위하여 두가지의 원반 간격에서 측정된 실험 자료를 이용하여 벽면 슬립을 보정하는 방법을 채택하였다. 실험 중, 측정 전단율범위를 제한하는 Thixotropy 현상을 발견학고 이에대한 원인분석을 위한 실험을 진행한 결과 과도한 전단응력에 의해서 분말사출재로부터 분리되어 나온 슬립층이 내부로 빠르게 흡수되어 들어가지 못하고 잔류하면서 Thixotropy 현상을 발 생시키는 것으로 판단되었다. Thixotropy 현상이 발생하지 않는 범위를 조사한후, 제한된 범위내에서 분말사출재의 유변학적 특성을 측정하였다. 측정된 자료는 항복응력을 지니는 유체의 특성을 표현하는 Bingham 식의 변형식에 잘 근사 되었으며, 슬립속도를 실험결과로 부터 계산한 결과 전단응력에 따라 선형적인 관계를 가지고 있는 점과 항복응력의 존재를 정성적으로 보여주는 결과를 얻었다.