• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.681-688
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• 2003

Rock damage induced by blasting can not be avoided during tunnel construction and may affect tunnel stability. But the mutual interaction between tunnel blasting design and tunnel stability design is generally not considered. Therefore this study propose a methodology to take into considration the results of the blasting damage in tunnel stability design. Rock damage is evaluated by dynamic numerical analysis for the most common blasting pattern adopted in road tunnel. Damage zone is determined by using the continuum damage model which is expressed as a function of volumetric strain. And the damage effect is taken into account by the damaged rock stiffness and the damaged failure criteria in tunnel stability assessment. The extend of plastic zone and deformation increase compared to the case of not considering blast-induced rock damage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.751-759
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• 1994

Concrete contains numerous microcracks initially. The growth and propagation of microcracks cause failure of concrete. These processings are termed as "damage". The concepts of the continuum damage mechanics are presented and the damage evolution law and constitutive equation are derived by using the Helmholz free energy and the dissipation potential by means of the thermodynamic principles. The constitutive equation includes the effects of elasticity, damage and plasticity of concrete. The proposed model successfully predicts the nonlinear behavior of concrete subject to monotonic uniaxial and biaxial loadings.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.475-502
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• 2016

Nanobeams are widely used as a structural element for nanodevices and nanomachines. The development of nano-sized machines depends on proper understanding of mechanical behavior of these nano-sized beam elements. Small length scales such as lattice spacing between atoms, surface properties, grain size etc. are need to be considered when applying any classical continuum model. In this study, Eringen's nonlocal elasticity theory is incorporated into classical beam model considering the effects of axial extension and the shear deformation to capture unique static behavior of the nanobeams under continuum mechanics theory. The governing differential equations are obtained for curved beams and solved exactly by using the initial value method. Circular uniform beam with concentrated loads are considered. The displacements, slopes and the stress resultants are obtained analytically. A detailed parametric study is conducted to examine the effect of the nonlocal parameter, mechanical loadings, opening angle, boundary conditions, and slenderness ratio on the static behavior of the nanobeam.

• Structural Engineering and Mechanics
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• v.83 no.3
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• pp.377-386
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• 2022

This paper considers dynamic impedance functions and presents a detailed analysis of the soil plasticity influence on the pile-group foundation dynamic response. A three-dimensional finite element model is proposed, and a calculation method considering the time domain is detailed for the nonlinear dynamic impedance functions. The soil mass is modeled as continuum elastoplastic solid using the Mohr-Coulomb shear failure criterion. The piles are modeled as continuum solids and the slab as a structural plate-type element. Quiet boundaries are implemented to avoid wave reflection on the boundaries. The model and method of analysis are validated by comparison with those published on literature. Numerical results are presented in terms of horizontal and vertical nonlinear dynamic impedances as a function of the shear soil parameters (cohesion and internal friction angle), pile spacing ratio and frequencies of the dynamic signal.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.389-393
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• 2002

• Steel and Composite Structures
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• v.36 no.3
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• pp.293-305
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• 2020

This article presented a nanoscale modified continuum model to investigate the free vibration of functionally graded (FG) porous nanobeam by using finite element method. The main novelty of this manuscript is presenting effects of four different porosity models on vibration behaviors of nonlocal nanobeam structure including size effect, that not be discussed before The proposed porosity models are, uniform porosity distribution, symmetric with mid-plane, bottom surface distribution and top surface distribution. The nano-scale effect is included in modified model by using the differential nonlocal continuum theory of Eringen that adding the length scale into the constitutive equations as a material parameter constant. The graded material is distributed through the beam thickness by a generalized power law function. The beam is simply supported, and it is assumed to be thin. Therefore, the kinematic assumptions of Euler-Bernoulli beam theory are held. The mathematical model is solved numerically using the finite element method. Results demonstrate effects of porosity type, material gradation, and nanoscale parameters on the free vibration of nanobeam. The proposed model is effective in vibration analysis of NEMS structure manufactured by porous functionally graded materials.

• Structural Engineering and Mechanics
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• v.40 no.2
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• pp.257-277
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• 2011

In this paper the geometrically nonlinear continuum plate finite element model, hitherto not reported in the literature, is developed using the total Lagrange formulation. With the layerwise displacement field of Reddy, nonlinear Green-Lagrange small strain large displacements relations (in the von Karman sense) and linear elastic orthotropic material properties for each lamina, the 3D elasticity equations are reduced to 2D problem and the nonlinear equilibrium integral form is obtained. By performing the linearization on nonlinear integral form and then the discretization on linearized integral form, tangent stiffness matrix is obtained with less manipulation and in more consistent form, compared to the one obtained using laminated element approach. Symmetric tangent stiffness matrixes, together with internal force vector are then utilized in Newton Raphson's method for the numerical solution of nonlinear incremental finite element equilibrium equations. Despite of its complex layer dependent numerical nature, the present model has no shear locking problems, compared to ESL (Equivalent Single Layer) models, or aspect ratio problems, as the 3D finite element may have when analyzing thin plate behavior. The originally coded MATLAB computer program for the finite element solution is used to verify the accuracy of the numerical model, by calculating nonlinear response of plates with different mechanical properties, which are isotropic, orthotropic and anisotropic (cross ply and angle ply), different plate thickness, different boundary conditions and different load direction (unloading/loading). The obtained results are compared with available results from the literature and the linear solutions from the author's previous papers.

• Advances in nano research
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• v.14 no.6
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• pp.521-525
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• 2023

This paper concerned with the vibration of double walled carbon nanotubes (CNTs) as continuum model based on Timoshenko-beam theory. The vibration solution obtained from Timoshenko-beam theory provides a better presentation of vibration structure of carbon nanotubes. The natural frequencies of double-walled CNTs against half axial wave mode are investigated. The frequency decreases on decreasing the half axial wave mode. The shape of frequency arcs is different for various lengths. It is observed that model has produced lowest results for C-F and highest for C-C. A large parametric study is performed to see the effect of half axial wave mode on frequencies of CNTs. This numerically vibration solution delivers a benchmark results for other techniques. The comparison of present model is exhibited with previous studies and good agreement is found.

• Journal of Families and Better Life
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• v.21 no.6
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• pp.53-67
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• 2003

The aim of this research is to verify the assumption that the husband-to-wife violence lies upon a continuum of severity and to study how the premarital violence experience of husbands, along with their psychological characteristics and various marital interactions, can be the cause of husbands' violence against their wives. At the same time, the research aims at constructing a causal model of the husband-to-wife violence. For the purpose, this research surveyed 242 husbands residing in Pusan and another 50 husbands as violent assaulters in major cities of Korea. The following is a summary of the results of this research. First, the research can verify the two assumptions that “the group which has once inflicted a severe form of violence can easily inflict minor violences” and that “the factors related to violence play a far greater role in severe violences than in weaker violences.” As a result, it may be concluded that the study of a regular household violence can be based on the continuum of violence assumption. Secondly, In the husbands' experience of violence, dating violence and their experienced childhood abuse from their parents, in their psychological characteristics, temper control ability and their patriarchal sex role attitude, and finally in marital interactions, marital conflicts and distractor of communication played great role in their influence on the husband-to-wife violence. Thirdly, as the various factors which contribute to the violence against the wife have cause-and-effect rule, we shall be able to make a model which can be conceptualized.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.9
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• pp.766-774
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• 2017

When a plume flow exhausted from a lunar lander descent engine impinges on the lunar surface, regolith particles on the lunar surface will be dispersed due to a plume-surface interaction. If the dispersed particles collide with the lunar lander, some adverse effects such as a performance degradation can be caused. Thus, this study tried to predict the plume flow behaviors using the CFD methods. A nozzle inside region was analyzed by a continuum flow model based on the Navier-Stokes equations while the plume behaviors of the outside nozzle was performed by comparing and analyzing the individual results using the continuum flow model and the DSMC method. As a result, it was possible to establish an optimum procedure of the plume analysis for the lunar lander descent engine in the vacuum condition. In the future, it is expected to utilize the present results for the development of the Korean lunar lander.