• The Journal of Engineering Geology
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• v.29 no.3
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• pp.315-327
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• 2019

Back analysis has been used to evaluate the factor of safety and circular failure plane at the landfill failure site. However, the estimated circular failure plane by back analysis is quite different from what is observed in the field. Thus, this study was conducted to estimate an actual shear failure plane inside the ground which gives a more accurate failure plane. Cone penetration test (CPT), boring test, soft X-ray image scan, density logging, and ultrasonic logging were conducted at the field and laboratory. The result of CPT showed significantly lower cone resistance, pore pressure, and undrained shear strength at a particular part. This part is a possible shear failure plane inside the ground. To validate, the soft X-ray scan images were analyzed and found the disturbed (inclined) bedding plane induced by shear activity at the estimated shear failure plane. Density and ultrasonic logging tests also found a similar result. Thus, the method in this study is possible to estimate the shear failure plane inside the ground.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.137-144
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• 2005

A direct shear test is classified roughly by one side simple shear test of confining horizontal displacement type and torsional shear test of non-confining one. Direct shear test that has been widely used so far has some problems with test apparatus, testing and the analysis, and in particular that its strength value is everestimated in sandy soils. Also, progressive failure of shearing process happens from shear apparatus restriction and because the shear strain and shear stress are erratic in specimen, we can not define the shear strain value. In the meantime, a simple shear test having advantage of direct shear test is an ideal test method that can get stress-strain relation on shear because it can deliver constant shearing deformation to specimen. However, simple shear test cannot be used practically, because its structure makes tester manufacturing difficult. This paper described a on outline of test apparatus, improvement of test method, and constant pressure test results based on the obtained from improved direct shear apparatus and the standardization of JGS soil testing method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.4
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• pp.209-216
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• 1998

본 논문에서는 부채꼴형 Mindlin 평판의 엄밀한 휨진동해를 제시하였다. 진동변위의 두 가지 적합 함수식, 즉 대수삼각다항식과 Mindlin 모서리함수를 Ritz방법에 적용하였다. 모서리함수는 부채꼴형 평판의 둔각 정점부에 존재하는 모멘트와 전단력의 특이도를 동시에 고려하고 있다. 이러한 모서리함수는 진동수의 수렴속도를 가속화한다. 본 연구에서는 부채꼴형 각도의 범위와 두께 비에 따른 엄밀한 진동수 및 수직진동 변위의 전형적인 등고선을 제시하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.63-74
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• 2008

Site response analyses were performed based on equivalent linear technique using the local geologic and dynamic site characteristics, which include soil profiles, shear wave velocity profiles and depth to bedrock for 125 sites collected in Korean Peninsula. From the results of site response analyses, 2-parameters site classification system based on the combination of mean shear wave velocity of soil and depth to bedrock was newly recommended for regions of shallow bedrock depth in Korea. First, as the borders of bedrock depth (H) for site classification were determined as 10m and 20m, the soil sites were divided into 3 classes as $H_1$, $H_2$ and $H_3$ sites. And then, the 3 site classes were subdivided into 7 classes based on the mean shear wave velocity of soil ($V_{s,soil}$). The feasibility of new site classification system was verified and the representative site coefficients ($F_a$ and $F_v$) and design response spectrum were suggested by analyzing uniform trend and dispersion of site coefficients for each site class. The suggested site coefficients and the regression curves present the nonlinear characteristics of soils according to the change of rock outcrop acceleration with uniform trend effectively. From the comparison between the mean values of response spectrum which was acquired from the site response analysis and the suggested design response spectrum, there was a little difference in some of site classes and it was verified to adjust the integration interval to make it more suitable for the site condition in Korea.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.132-140
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• 1995

The structural behavior of sandwich plates with unsymmetricaly thick faces are analysed using Raleigh-Ritz Energy method by comparing the bending stresses, shear stresses, local bending stresses, membrane stresses of skin and core materials including local bending effect. As for sandwich materials, the combination of two types of face materials and three types of core materials are used in the analysis.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.151-160
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• 2003

The stability of the designed rock slope is analysed based on two kinds of shear strength model. Besides the deterministic analysis, a probabilistic approach on Monte Carlo simulation is proposed to deal with the uncertain characteristics of the discontinuity and the results obtained from two models are compared to each other. To carry out the research of characteristics of the discontinuity, BIPS, DOM Scanline survey data and direct shear test data are used, and chi-square test is used for determining the probability distribution function. The rock slope is evaluated to be stable in the deterministic analysis, but in the probabilistic analysis, the probability of failure is more than 5%, so, it is considered that the rock slope is unstable. In the shear strength models, the probability of the failure based on the Mohr-Coulomb model(linear model) is higher than that of the Barton model. It is supported by the fact that the Mohr-Coulomb model is more sensitive to block size than the Barton model. In fact, there is no reliable way to estimate the unit cohesion of the Mohr-Coulomb model except f3r back analysis and in the case of small block failure in the slope, Mohr-Coulomb model may excessively evaluate the factor of the safety. So, the Barton model of which parameters are easily acquired using the geological survey is more reasonable for the stability of the studied slope. Also, the selection of the proper shear strength model is an important factor for slope failure analysis.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.136-152
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• 1993

This study is intended to develop an accurate and efficient, analytical thin-walled beam model, and to analyze overall behavior of SWATH ship under repeated overloads. SWATH ship is idealized to a simple thin-walled beam of channel type. An analytical beam model is formulated by the stress component with geometrically(fully) nonlinear thin-walled beam and treated numerically by the Finite Element Method. An efficient cyclic plasticity model is also included, suitable for material nonlinear behavior under complex loading conditions. The local stress distribution can be very exactly represented and the material yielding propagation, easily traced. In addition, the local treatment of the effect of shear deformation improves the representation of deformation and shear stress distribution along the section contour. It is desirable to use the analytical thin-walled beam at initial design stage, and is needed to improve the practical thin-walled beam model advancing the current approach.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.26-34
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• 2019

In this paper, a coarse lunar soil model is developed using discrete element method and its computed physical properties are compared with those of the actual lunar soil for its validation. The surface of the actual moon consists of numerous craters and rocks of various sizes, and it is covered with fine dry soil which seriously affects the landing stability of the lunar lander. Therefore, in consideration of the environment of the lunar regolith, the lunar soil is realized using discrete element method. To validate the coarse model of lunar soil, the simulations of the indentation test and the direct shear test are performed to check the physical properties(indentation depth, cohesion stress, internal friction angle). To examine the performance of the proposed model, the drop simulation of finite element model of single-leg landing gear is performed on proposed soil models with different particle diameters. The impact load delivered to the strut of the lander is compared to test results.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.105-113
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• 1999

This paper resents a prediction method of natural frequencies of coupled horizontal and torsional vibration of hull girder based on design sensitivity analysis in case of the changes of system parameters. The sensitivity analysis is formulated applying the direct differentiation method and transfer matrix method. In the analysis, warping, shear deformation due to torsion and the continuity condition at the connected part of open and closed hull section are considered. Using the presented method. The affection for natural frequencies by the change of system parameters, especially cargo and added mass and their centers, is numerically investigated for a real large container carrier.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.141-154
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• 1993

In this paper, a method to calculate the ultimate compressive strength of welded one-sided stiffened plates simply supported along all edges is proposed. At first initial imperfections such as distortions and residual stresses due to welding are predicted by using simplified methods. Then, the collapse modes of the stiffened plate are assumed and collapse loads for each mode are calculated. Among these loads, the lowest value is selected as the ultimate strength of the plate. Collapse modes are assumed as follows ; (1) Overall buckling of the stiffened plate$\rightarrow$Overall collapse due to stiffener bending (2) Local buckling of the plate part$\rightarrow$Local collapse of the plate part$\rightarrow$Overall collapse due to stiffener yielding (3) Local buckling of the plate part$\rightarrow$Overall collapse due to stiffener berthing (4) Local buckling of the plate part$\rightarrow$Local collapse of the plate part$\rightarrow$Overall collapse due to stiffener tripping. The elastic large deflection analysis based on the Rayleigh-Ritz method is carried out, and plastic analysis assuming hinge lines is also carried out. Collapse load is defined as the cross point of the two analysis curves. This method enables the utimate strength to be calculated with small computing time and a good accuracy. Using the present method, characteristics of the stiffener including torsional rigidity, bending and tripping can also be clarified.