• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.817-820
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• 2008

이 논문은 초고강도 섬유보강 I형 보의 거동을 Diana를 사용하여 3차원 유한요소해석을 수행하였다. 보통 또는 고강도 콘크리트의 구성방정식과 달리 초고강도 섬유보강 콘크리트의 재료적 특성 즉, 인장 변형률 강화를 고려한 탄-소성 파괴 역학적 모델을 제안하여 해석에 반영하였다. 인장영역에서는 인장 변형률 강화를 고려한 다차원 고정 균열 규준을 사용하였고, 압축영역에서는 associated flow rule을 고려한 Drucker-Prager Criterion을 채택하였다. UHPFRC(Ultra-High Performance Fiber Reinforced Concrete) I형 보의 하중변형관계, 최초 균열, 최초 대각 균열, 극한상태 등의 결과를 실험결과와 비교하여 해석법의 유용성을 입증하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.649-659
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• 2002

For a variety of elastic-plastic stress fields of plane strain specimens, many research works verified the validity of J-T approach. To generalize the validity of J-T method, however, further investigations are needed for more practical 3D structures than the idealized geometries as plane strain specimens. In this work, selecting two main types of structures such as plate and straight pipe, we perform 3D finite element(FE) modeling, and accompanying elastic, elastic-plastic FE analyses. We then study the validity of J-T application to 3D structures, and present some useful informations for the design or assessment of pipe welds by comparing the stress fields from the detailed 3D FE analyses to those predicted with J-T two parameters.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.437-447
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• 2016

In a nuclear power plant, the fuel assembly, which is composed of fuel rods, burns, and the high temperature can generate power. The fuel rod consists of pellets and a cladding that covers the pellets. It is important to understand the pellet-cladding mechanical interaction with regard to nuclear safety. This paper proposes simulation of the PCMI. The gap between the pellets and the cladding, and the contact pressure are very important for conducting thermal analysis. Since the gap conductance is not known, it has to be determined by a suitable method. This paper suggests a solution. In this study, finite element (FE) contact analysis is conducted considering thermal expansion of the pellets. As the contact causes plastic deformation, this aspect is considered in the analysis. A 3D FE module is developed to analyze the PCMI using FORTRAN 90. The plastic deformation due to the contact between the pellets and the cladding is the major physical phenomenon. The simple analytical solution of a cylinder is proposed and compared with the fuel rod performance code results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.04a
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• pp.17-27
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• 1995

For the post-buckling and elasto-plastic analysis of shell structures, the total Lagrangian formulation is presented based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors in the iteration process and evaluating the total Green-Lagrange stain corresponding U total displacements. In the calculation of the stiffness matrix, the element formulation takes into account the effect of finite rotation increments by retaining second order rotation terms in the incremental displacement field. The selective or reduced integration scheme using the heterosis element is applied in order to overcome both shear locking phenomena and the zero energy mode. The load/displacement incremental scheme is adopted for geometric non-linear F .E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with references's results.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.149-157
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• 2004

Residual stresses can have a significant influence on the fatigue lives of structural engineering components. For the accurate assessment of fatigue lifetimes a detailed knowledge of the residual stress profile is required. Significant advances have been made in recent years fur obtaining accurate and reliable determinations of residual stress distributions. These include both experimental and numerical methods. The purpose of this study is to simulate peening process with the help of the finite element method in order to predict the magnitude and distribution of the residual stresses in accordance with the parameters, which are, e.g. shot velocity, shot diameter, shot impact angle, shot shape, distance between two impinging shots, and material parameters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1229-1241
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• 1994

This study aims at investigating the undrained behavior of the normally consolidated clay foundation using single hardening constitutive model based on elasticity and plasticity theories. The specimen employed was sampled at Mooan near the down stream of Young San river and remolded into consolidation apparatus. 11 soil parameters for the model was determined from simple tests such as isotropic compression and consolidation undrained triaxial compression tests. FEM program to predict the undrained behavior of the foundation was developed and back analysis was performed to verify prediction ability of the FEM program. Finally plate load test on the 2-dimensional model foundation was carried out in order to compare numerical analysis and observed values on the foundation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.105-117
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• 1994

A finite element procedure which can trace plastic collapse behavior of plane frame structures under small and large deformation is presented. The member is assumed to be prismatic and straight, and has the rectangular or I cross section. For the elasto-plastic analysis, the concept of plastic hinge is introduced and the incremental displacement method is applied. The limit state condition of the plastic hinge is considered under the combined condition of a bending moment and an axial force. Numerical examples are presented in order to demonstrate the validity and efficiency of the proposed procedure.

• Geotechnical Engineering
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• v.3 no.4
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• pp.7-20
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• 1987

This study was performed to investigate the effect of time-dependent creep on the deformation analysis of multi-dimensional consolidation using the finite element method for young Sedimentary clay. It was assumed that the creep in the clay had occured during consolidation. In the analysis, the Modified cam-clay theory originated from the critical state theory was used as the constitutive equation, in which a term equivalent to the creep was supplemnted. The results of the analysis were in good agreement with the observed values in the field.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.89-94
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• 1996

The use of shield is increasing day by day, because it's method is advantageous tunneling method to soft and collapsible ground. In case of analyzing shield tunnel by FEM, short term behavior of ground by initial heaving and tail void closure and long terms of it because of consolidation by changes of pore pressures in clay must be considered. In this paper, the shield tunneling construction stages was analyzed from 2 dimensional elasto - viscoplastic finite element program used Mohr - Coulomb yield criterion but not considered the changes of pore pressures. The object of investigation was N - 2 Tunnel. Since the good results of analysis compared to the measured behavior of ground for heaving, tail void closure and liner installation, this results can be applied to design and construction of shield tunneling for the subways, sewage lines etc.