• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.261-267
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• 2014

Various types of external loads can be applied to the tunnel structure. In a shield tunnel, the vibration from the train may affect the behavior of the adjacent ground. In this study, the railway-induced vibration was estimated and applied to the shield tunnel through 3D numerical simulation. The effective stress analysis based on the finite difference method and Finn model was performed to investigate the potential of liquefaction below the tunnel. Furthermore, pore water pressure and displacement were monitored on a time domain; consequently, the liquefaction potential and dynamic response of the shield tunnel were analyzed. Consequently, it is confirmed that the generation of excess pore water pressure by train-induced vibrating load, however, the amount does not meaningfully affect the potential of liquefaction.

• Computational Structural Engineering
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• v.9 no.1
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• pp.65-76
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• 1996

The initiation and growth of microcracks or microvoids inside concrete results in the progressive degradation of concrete. This damage processing along processing along with plastic deformation is main cause of nonlinear behavior of concrete. In this study, a continuum damage model of concrete is developed for the analysis of the nonlinear behavior of concrete due to damage and elasto-plastic deformation. Anisotropic damage tensor is used to describe the anisotropy of concrete and hypothesis of equivalent elastic energy is used to define the effective elastic tensor. The damage model including the damage evolution law and constitutive equation is derived with damage variable and damage surface which is defined by damage energy release rate by using the Helmholtz free energy and dissipation potential based on the thermodynamic principles. By adopting a typical plasticity model of concrete, plasticity of concrete is included to this model. Afinite element analysis program implemented with this model was developed and finite element analysis was performed for the analyses of concrete subjected to uniaxial and biaxial loadings. Comparison of the results of analysis with those of experiments and other models shows that the model successfully predicts the nonlinear behavior of concrete.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.405-411
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• 2016

This paper presented the theory related to a two dimensional linear cross-sectional analysis, recovery relationship and a one-dimensional nonlinear beam analysis for composite beam with initial twist and high aspect ratio. Using VABS including related theory, preceding research data of the composite wing structure has been modeled and compared. Cross-sectional analysis was performed and 1-D beam was modeled at cutting point including all the details of real geometry and material. The 3-D strain distribution and margin of safety at recovery point was calculated based on the global behavior of the 1-D beam analysis and visualize numerical results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1521-1528
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• 2011

We studied the material properties for reliability improvement in finite element analysis results for a nitrile butadiene rubber hub-bearing seal and for a carbon-filled rubber mount used in a vehicle. It was difficult to measure the material properties of hundreds of types of rubber for the mount design. Thus, we suggested that the engineering stressstrain relations from pure shear test data could be synthesized by using simple tension data and Poisson's ratio. We defined Poisson's ratio by using a function of principal stretches to synthesize the stress-strain relations for a pure shear test. A transformation of the pure shear data was applied to the experimental values to obtain the predicted results when the strain approaches 100%. In the finite element analysis for the contact force of a hub-bearing seal, the strain results that used the transformation of the pure shear data and simple tension data almost corresponded to the experimental values. Ogden constants were used to analyze.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.141-150
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• 2017

Geosynthetics are generally utilized to restrain the leakage of leachate and other contaminants during the construction of offshore waste landfill. Therefore, geosynthetic-soil interface is formed inevitably. In this study, 2 dimensional numerical analysis is performed to assess the dynamic behaviour of the offshore waste landfill including geosynthetic-soil interface. Offshore waste landfill can be divided into rubble mound revetment and retaining wall types and analyzed on each type. Effective stress analysis is conducted to consider the variation of pore water pressure and axial force and shear displacement of the interface are compared based on the characteristics of seismic frequency. Consequently, retaining wall type demonstrates more stable behavior against liquefaction potential and favorable forces and shear displacement.

• Journal of the Korea Concrete Institute
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• v.13 no.4
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• pp.379-388
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• 2001

Existing microplane models for concrete use three-dimensional spherical microplanes in the analysis of two-dimensional planar members as well as three-dimensional members. Also, they do not accurately describe the post-cracking behavior of reinforced concrete in tension-compression. In this study, a new microplane model is developed to overcome the disadvantages of the existing models. Instead of the spherical microplanes, the proposed microplane model uses disk microplanes involving a less number of microplanes and two-dimensional stresses and strains. As the result, the proposed model is more effective in numerical calculations. Also, the concept of the strain boundary is introduced to describe accurately the compressive behavior of reinforced concrete with tensile cracks in tension-compression. The validity of the proposed model is verified by comparison with existing experiments. In this paper, the microplane model and the numerical techniques involved in the finite element analysis are described in detail.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.23-28
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• 2019

The structural integrity of a surface metal coating was evaluated through numerical results to improve the efficiency and reduce the damage caused by cavitation in ships and marine plants. The goal was to ensure structural strength and performance, even if the thickness of the wing is reduced to reduce the weight of the material and surface coating. Analytical methods were used for four models: a non-coating model, one with the same thickness after coating, one with a thickness reduction of 3% after coating, and one with thickness reduction of 5% after coating. With a thickness reduction of 5% after coating, the stress was increased to 12%, and the safety factor was 0.99%, so the structural integrity was insufficient. However, a better material or a thicker coating could allow a sufficient safety factor to be secured. The structural integrity was improved by the coating, and even when the weight was reduced up to 5%, the structural integrity could be sufficiently secured due to the coating effect.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.47-56
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• 2001

In the present study, mainly to determine the embarkation time of equipment in dredged clay fills, an analytical approach is performed to predict a variation of the undrained shear strength in the outermost layer. In this approach, Gibson's non-dimensional linear constant defining the relationship between the void ratio and the effective stress is employed. Also in this approach, void ratios and settlements associated with the volume change due to the self-consolidation and the desiccation shrinkage are evaluated at various elapsed times based on the finite difference solution technique proposed by the authors(1999) and the developed computer program named as DSCON. Predicted results(water content ratio, unit weight and undrained shear strength) are compared with those of laboratory model tests conducted with soil samples obtained from the Koheung site. Based on the predicted undrained shear strengths, possible embarkation time of a equipment is also evaluated. In addition, further analyses are made to indirectly verify the efficiency of the analytical approach proposed in the present study using the PSDDF computer program which can consider the drainage efficiency.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.1
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• pp.20-35
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• 2017

In the case of the seabed around and under gravity structures such as submerged breakwater is exposed to a large wave action long period, the excess pore pressure will be significantly generated due to pore volume change associated with rearrangement soil grains. This effect will lead a seabed liquefaction around and under structures as a result of the decrease in the effective stress, and eventually the possibility of structure failure will be increased. The study of liquefaction potential for regular waves had already done, and this study considered for irregular waves with the same numerical analysis method used for regular waves. Under the condition of the irregular wave field, the time and spatial series of the deformation of submerged breakwater, the pore water pressure (oscillatory and residual components) and pore water pressure ratio in the seabed were estimated and their results were compared with those of the regular wave field to evaluate the liquefaction potential on the seabed quantitatively. Although present results are based on a limited number of numerical simulations, one of the study's most important findings is that a safer design can be obtained when analyzing case with a regular wave condition corresponding to a significant wave of the irregular wave.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.4
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• pp.177-190
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• 2016

In case of the seabed around and under gravity structures such as submerged breakwater is exposed to a large wave action long period, the excess pore pressure will be generated significantly due to pore volume change associated with rearrangement soil grains. This effect will lead a seabed liquefaction around and under structures as a result from decrease in the effective stress. Under the seabed liquefaction occurred and developed, the possibility of structure failure will be increased eventually. Lee et al.(2016) studied for regular waves, and this study considered for irregular waves with the same numerical analysis method used for regular waves. Under the condition of the irregular wave field, the time and spatial series of the deformation of submerged breakwater, the pore water pressure (oscillatory and residual components) and pore water pressure ratio in the seabed were estimated and their results were compared with those of the regular wave field to evaluate the liquefaction potential on the seabed quantitatively. Although present results are based on a limited number of numerical simulations, one of the study's most important findings is that a more safe design can be obtainable when analyzing case with a regular wave condition corresponding to a significant wave of irregular wave.