• 한국지진공학회논문집
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• 제9권4호
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• pp.67-74
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• 2005

이 논문에서는 포화된 2상 지반의 동적해석에서 원역을 모형화하기 위한 새로운 무한요소를 제안하였다. 무한요소법은 무한영역 또는 반무한영역을 모형화해야 하는 공학문제에 효과적으로 적용되어 왔다. 그러나 현재까지 개발된 2상지반의 동적해석을 위한 무한요소는 형상함수에 사용될 수 있는 파동성문이 2개(Pl파와 P2파)로 한정되어 있다. 이 논문에서는 이와 같은 제한을 없애고 임의 개수의 파동성분을 고려할 수 있도록 하는 정식화 과정을 제안하였다. 구조물을 포함하는 근역은 유한요소로 나타내며 원역은 평행층상 반무한 지반으로 가정하였다. 제안된 무한요소의 타당성은 1차원 및 2차원 파동전달문제를 해석하고 이를 이론해 및 정밀수지해석 해와 비교하여 검증하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.34-41
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• 2005

This paper presents a new infinite element for modeling far-field of wave propagation problem in a fluid-saturated two-phase medium. The infinite element can simulate arbitrary number of multiple wave components, while wave components in infinite element developed by other researchers was limited to two compressional waves. The accuracy and effectiveness of the proposed method have demonstrated using 1-D and 2-D wave propagation problems.

• Journal of Mechanical Science and Technology
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• 제16권5호
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• pp.655-665
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• 2002

Two-dimensional elastic analysis of doubly periodic circular holes in an infinite plane is given in this paper. Two cases of loading, remote tension and remote shear, are considered. A rectangular cell is cut from the infinite plane. In both cases, the boundary value problem can be reduced to a complex mixed one. It is found that the eigenfunction expansion variational method is efficient to solve the problem. Based on the deformation response under certain loading, the notched medium could be modeled by an orthotropic medium without holes. Elastic properties for the equivalent orthotropic medium are investigated, and the stress concentration along the hole contour is studied. Finally, numerical examples and results are given.

• Structural Engineering and Mechanics
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• 제21권1호
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• pp.67-82
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• 2005

This study analyzes stress intensity factors for a number of periodic edge cracks in a semiinfinite medium subjected to a far field uniform applied load along with a distribution of eigenstrain. The eigenstrain is considered to be distributed arbitrarily over a region of finite depth extending from the free surface. The cracks are represented by a continuous distribution of edge dislocations. Using the complex potential functions of the edge dislocations, a simple as well as effective method is developed to calculate the stress intensity factor for the edge cracks. The method is employed to obtain the numerical results of the stress intensity factor for different distributions of eigenstrain. Moreover, the effect of crack spacing and the intensity of the normalized eigenstress on the stress intensity factor are investigated in details. The results of the present study reveal that the stress intensity factor of the periodic edge cracks is significantly influenced by the magnitude as well as distribution of the eigenstrain within the finite depth. The eigenstrains that induce compressive stresses at and near the free surface of the semi-infinite medium reduce the stress intensity factor that, in turn, contributes to the toughening of the material.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.145-152
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• 1994

The dynamic interaction between tunnel structures and their surrounding soil medium due to impulse loading is investigated by a hybrid IEM/FEM methodology. A dynamic infinite element is developed for the efficient descretization of the far-field region of the unbounded soil medium. The shape functions of the infinite element are constructed based on the far-field solutions which are obtained by solving the 2-D elastic wave problems. Also they are devised to obtain a reasonable result over all frequency range. Numerical analysis is carried out to examine the response of the tunnel subjected to simple rectangular impulse. It is indicated that the results by the present method are in good accord with those by the boundary and finite element coupling method.

• The Journal of the Acoustical Society of Korea
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• 제17권1E호
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• pp.70-75
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• 1998

The analysis of dynamic responses are carried out on several anisotropic systems due to buried pulsating line sources. These include infinite, semi-infinite spaces. The media possess orthotropic or higher symmetry. The load is in the from of a normal stress acting with parallel to symmetry axis on the plane of symmetry within the materials. The results are first derived for infinite media. Subsequently the results for semi-infinite are derived by using superposition of the solution in the infinite medium together with a scattered solution from the boundaries. The sum of both solutions has to satisfy stress free boundary conditions, thereby leading to the complete solutions. The solutions are simplified to the systems possessing of higher symmetry, such as orthotropic, transversely isotropic, cubic, and isotropic symmetry.

• 한국지반공학회지:지반
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• 제13권1호
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• pp.101-110
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• 1997

본 논문에서는 무한영역에서 발생하는 임의의 1$1/r^n$변위감쇠특성을 해석할 수 있는 p-버전 정적 무한요소를 연구하였다. 무한요소를 개발하기 위하여 이론해를 근사화한 형상함수를 사용하였다. 균질한 무한 탄성체내의 공동변형문제와 반무한탄성체위에 놓인 강성기초의 거동해석을 통하여, 본 연구에서 개발된 무한요소가 무한영역을 효율적으로 묘사할 수 있음을 검토하였다.

• 소음진동
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• 제8권5호
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• pp.974-980
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• 1998

본 논문은 직교이방성 탄성계에서 내부 선형하중에 의한 탄성파의 거동을 고찰하였다. 첫째로, 내부 발진원에 대한 탄성과 거동식을 무한계와 반구계에서의 직교이방성 매체에서 유도하였고, 둘째로 Cargniard-DeHoop을 이용하여 순간선형하중에 대한 무한계와 반구계에서의 탄성과 거동식을 유도하였다. 반구계에서 탄성파에 대한 거동식은 무한계에서 유도한 결과와 반구의 표면에서 분산되는 반사파의 합으로 표현되고, 경계영역에서 경계조건을 만족하였다. 여러 가지 이방성 매체에 대한 수치해석 결과를 제시하였고, 이방성 매체의 특성인 bulk wave의 Lacunae 및 표면파의 영향을 고찰할 수 있었다. 본 논문의 결과는 지진연구, 복합소재 특성 연구, 지능형소재 특성연구 등에 응용될 것이다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.137-144
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• 1994

In this study, a new procedure for solving 2-D dynamic problems of semi-infinite medium in time domain by boundary element method (BEM) is presented. Efficient modelling of the far field region, infinite boundary elements are introduced. The shape function of the infinite boundary element is a combination of decay functions and Laguerre functions. Though the present shape functions have been developed for the time domain analysis, they may be also applicable to the frequency domain analysis. Through the response analysis in a 2-D half space under a uniformly distributed dynamic load, it has been found that an excellent accuracy can be achieved compared with the analytical solution

• Interaction and multiscale mechanics
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• 제1권1호
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• pp.157-175
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• 2008

A brief review of the research works on ground vibrations caused by trains moving in underground tunnels is first given. Then, the finite/infinite element approach for simulating the soil-tunnel interaction system with semi-infinite domain is summarized. The tunnel is assumed to be embedded in a homogeneous half-space or stratified soil medium. The train moving underground is modeled as an infinite harmonic line load. Factors considered in the parametric studies include the soil stratum depth, damping ratio and shear modulus of the soil with or without tunnel, and the thickness of the tunnel lining. As far as ground vibration is concerned, the existence of a concrete tunnel may somewhat compensate for the loss due to excavation of the tunnel. For a soil stratum resting on a bedrock, the resonance peak and frequency of the ground vibrations caused by the underground load can be rather accurately predicted by ignoring the existence of the tunnel. Other important findings drawn from the parametric studies are given in the conclusion.