• The Journal of Engineering Geology
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• v.30 no.1
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• pp.1-15
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• 2020

The Mohr-Coulomb model is mainly used in evaluating the behavior of the ground in numerical analyses of domestic ground excavation. This study analyzes its limitations and compares its numerical results with the hyperbolic model, a model that closely follows actual ground behavior during excavation. Recent applications of the Mohr-Coulomb model in Korea have tended to impose arbitrary special boundary conditions to control the problem of excessive heaving of the ground excavation surface. This adjustment only controls the size of the heaving of the excavation surface, implying that the ground behavior is distorted from the actual behavior. This study compares results from the hyperbolic model (hardening soil model) and the Mohr-Coulomb model, and confirms that the hyperbolic model provides both a more-suitable solution to the problem of heaving during excavation and the actual stress-strain behavior. In numerical analyses of ground excavation, the hyperbolic model is expected to give results consistent with the actual ground behavior.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.216-224
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• 2011

In this study, Class II behavior of rock failure process under uniaxial and biaxial compression has been numerically simulated using bonded particle model. Class II behavior of rock was simulated by radial strain controlled uniaxial and biaxial compression tests using a suggested method of ISRM. Micro-parameters used in the simulation were determined based on the laboratory uniaxial compression tests carried out at ${\"{A}}sp{\"{o}}$ Hard Rock Laboratory, Sweden. Class II behavior of ${\"{A}}sp{\"{o}}$ rock was effectively simulated using newly proposed numerical technique in this study, and the results of numerical simulations show good similarity with the complete stress-strain curves for Class II behavior obtained from the laboratory tests.

• Tunnel and Underground Space
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• v.14 no.4
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• pp.287-294
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• 2004

To predict the temperature distribution around a underground rock storage cavern, two- and three- dimensional numerical analysis using FLAC was conducted. The effects of groundwater and latent heat on thermal properties were considered in numerical calculation. The temperature estimated by FLAC are compared with the temperature measured for 5-year operation at Gonjiam storage cavern. Estimated and measured temperatures showed great discrepancy when thermal properties from laboratory tests were used and showed good agreement when the effects from 20% of volumetric water fraction and latent heat were considered. However, the discrepancy still increased with operation time due to the heat flow from ground surface. Three-dimensional numerical models were established to closely approximate the boundary condition of the test site, and numerical results better agreement when groundwater and latent heat effects were considered.

• Fire Science and Engineering
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• v.25 no.6
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• pp.58-63
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• 2011

This study is intended to present a computational thermal model for the combustibles in a residential building. As the Performance Based Design is more popular, fire-intensity and fire-load have turned out to be very important factors for building design and can be predicted through some computational work. To predict and estimate the thermal properties of the residential combustible fire, we made some numerical models of combustibles in a residential building. In a bid to validate the estimate values, computational analysis results from numerical models were compared with real fire tests. For computational analysis, the Fire Dynamics Simulator was used with Large Eddy Simulation model for turbulence. Consequently, each heat release rate and total heat release curves were successfully estimated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.451-458
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• 2004

The study was focused on the development of computational scheme in three dimensional configurations by applying effective heat capacity model to the numerical procedure in order to predict the temperature profiles of a buried pipeline and the frozen penetration depth(FPD) of a freezing soil medium. To realize this, the investigator conducted the unsteady state heat transfer analysis, using the commercial code ABAQUS, for the freezing granite soil medium including a pipeline in a closed system. The proposed model took into consideration the phase change effect of in situ pore water in the frozen fringe. The comparison of results obtained by the proposed model and the actual performances was valuable in establishing a level of confidence in the application of introduced theory.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.231-236
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• 2008

A method of moments model for the resistive vee dipole has been established. In order to validate the numerical model, an experimental model is built and reflections from the antenna in the feed line are measured. The measured data and the numerical data agree closely validating the numerical model. Based on the numerical model, efficiency of the antenna and the power dissipated in the resistors are analyzed. The results show that the antenna has low radiation efficiency because of the loading resistors and that the resistors near the drive point of the antenna dissipate more power than do the resisters far from the drive point. The results can be used to determine the amount of power that can be accepted by the resistive vee dipole, to determine the power rating of the loading resistors for a desired application, or to estimate the operation range of the antenna.

• Journal of the Korean Wood Science and Technology
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• v.36 no.3
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• pp.24-29
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• 2008

Numerical analysis model was used to analyse the behaviors of multiple bolted connections. Axial-bending element was supposed as basic model, and the effects of frame members and steel fasteners were classified for the behavior analysis. In the condition only two bolts were used, the traditional analytical methods, which show somewhat accuracy, have some advantages more than numerical analysis that need many time consuming, However, more many bolts were used in practical field condition. Also, it is impossible to analyse the behaviors of various bolts layouts and arrangements conditions by traditional analytical methods. Therefore, there is only numerical analysis method for the accurate behavioranalysis on the practical bolted connection condition. Therefore, numerical analysis method was applied on the various multiple bolted connections. On the result exactness and the reflection of connection condition, numerical analysis method showed the superiority more than widely used traditional empirical analysis methods as yield model.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.117-128
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• 2000

The development of proper joint model, which can describe real phenomena exactly and still can be used easily, is one of the most important element for the analysis of the mechanical and hydraulic behavior of discontinuous rock mass. In this study, an elasto-plastic constitutive model of joint behavior considering asperity degradation was extended with the concept of first and second order asperities. The proposed model was implemented to numerical code with discrete finite joint element. The parametric study with the various asperity angles and degradation coefficients showed that the model can reproduce the shear behavior of typical rough joints well. Results of laboratory monotonic and cyclic shear tests were compared with those of numerical tests to validate the model. The hydraulic model considering the relations between gouge production and aperture was introduced to the mechanical model. In an attempt to examine the performance of the model, comparative numerical test was conducted. Permeability between joint surfaces increased rapidly at the first stage, but became nearly constant with increasing shear displacement due to gouge production and uniform variation of aperture distribution.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.366-377
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• 2000

The development of proper joint model, which can describe real phenomena exactly and still can be used easily, is one of the most important element for the analysis of the mechanical and hydraulic behavior of discontinuous rock mass. In this study, an elasto-plastic constitutive model of joint behavior considering asperity degradation was extended with the concept of first and second order asperities. The proposed model was implemented to numerical code with discrete finite joint element. The parametric study with the various asperity angles and degradation coefficients showed that the model can reproduce the shear behavior of typical rough joints well. Results of laboratory monotonic and cyclic shear tests were compared with those of numerical tests to validate the model. The hydraulic model considering the relations between gouge production and aperture was introduced to the mechanical mode1. In an attempt to examine the performance of the model, comparative numerical test was conducted. Permeability between joint surfaces increased rapidly at the first stage, but became nearly constant with increasing shear displacement due to gouge production and uniform variation of aperture distribution.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.88-94
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• 2022

The vibration mode measurement test measures the natural vibration characteristics of the target specimen. The measured natural mode characteristics are compared with the numerical analysis result to verify the reliability of the numerical analysis. If necessary, it is used to supplement the numerical analysis model of the specimen used for the dynamic characteristic analysis. In this paper, the natural frequency and natural mode of the external fuel tank are respectively obtained through the vibration mode measurement test and the numerical analysis, using the finite element model. The results are compared to verify the reliability of the numerical analysis model of the external fuel tank to apply to the entire aircraft model. To measure the vibration mode of the test specimen, a bungee cord was used, to simulate the free boundary condition for the test specimen. And, 3-axis accelerometers were installed on the test specimen. The response characteristics of the test specimen were measured, by excitation with an impact hammer. As a result of the test, after performing the frequency response analysis on the response acceleration, the natural frequency of the test specimen and its vibration mode were confirmed. The reliability of the numerical analysis model was verified by comparing the frequency and vibration mode, obtained through the test and the numerical analysis.