• Title, Summary, Keyword: infinite elements

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Time domain earthquake response analysis method for 2-D soil-structure interaction systems

  • Kim, Doo-Kie;Yun, Chung-Bang
    • Structural Engineering and Mechanics
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    • v.15 no.6
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    • pp.717-733
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    • 2003
  • A time domain method is presented for soil-structure interaction analysis under seismic excitations. It is based on the finite element formulation incorporating infinite elements for the far field soil region. Equivalent earthquake input forces are calculated based on the free field responses along the interface between the near and far field soil regions utilizing the fixed exterior boundary method in the frequency domain. Then, the input forces are transformed into the time domain by using inverse Fourier transform. The dynamic stiffness matrices of the far field soil region formulated using the analytical frequency-dependent infinite elements in the frequency domain can be easily transformed into the corresponding matrices in the time domain. Hence, the response can be analytically computed in the time domain. A recursive procedure is proposed to compute the interaction forces along the interface and the responses of the soil-structure system in the time domain. Earthquake response analyses have been carried out on a multi-layered half-space and a tunnel embedded in a layered half-space with the assumption of the linearity of the near and far field soil region, and results are compared with those obtained by the conventional method in the frequency domain.

무한요소(Infinite Elements)를 이용한 기초공학해석

  • 양신추
    • Computational Structural Engineering
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    • v.4 no.2
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    • pp.9-12
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    • 1991
  • 공학문제에 있어서, 해석적으로 접근할 수 없었던 많은 경우의 문제들이 유한요소법(Finite Element Methods)의 정형화된 모형화 및 해석과정을 통하여 쉽게 접근되어질 수 있었다. 최근 보다 효율적인 요소개발과 컴퓨터 기술의 발달로 유한요소법은 더욱 효과적인 해석 수단이 되어가고 있다. 그러나 지반공학 문제와 같은 무한영역 문제를 유한요소법으로 해석할 경우, 매우 큰 영역을 모형화하기 위하여 많은 수의 요소가 요구되며 이에 따른 자유도(Degree of Freedom) 수의 증가로 많은 계산시간을 요구하게 된다. 본 고는 무한영역 문제를 효과적으로 모형화하기 위하여 연구, 개발되어진 무한요소(Infinite Element)에 대하여 소개하려 한다. 무한요소의 기본개념과 강성행렬의 형성방법을 보인 후, 기초공학 문제를 예로 하여 이의 적용방법을 간략하게 설명하였다.

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On the Structure of A Matrix for Dynamic Stability Analysis of One Machine to the Infinite Bus (발전기-무한모선계통의 동태안정도 해석시 A행렬의 구조)

  • Kwon, Sae-Hyuk;Song, Kil-Yeong
    • Proceedings of the KIEE Conference
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    • pp.211-215
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    • 1989
  • The structure of A matrix of one machine connected to the infinite bus is described for a full model. The A matrix can be partitioned to submatrices which depend on the initial operating point and do not depend on it. When the dynamic properties for several different operating points are desired, those submatrices can be obtained through simple column operations. Furthermore, the elements of A matrix car be directly calculated from the manufacturer's data. RMS quantities of the state variables for the initial operating point are used. This approach can save the labor for calculating the elements of A matrix for the dynamic stability analysis.

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Time Domain Soil-Structure Interaction Analysis for Earthquake Loadings Based on Analytical Frequency-Dependent Infinite Elements (무한요소를 사용한 지반-구조물 상호작용계의 시간 영역 지진응답해석)

  • 김두기
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.107-112
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    • 1999
  • This paper presents a time domain method for soil-structure interaction analysis for seismic loadings. It is based on the finite element formulation incorporating analytical frequency-dependent infinite elements for the far-field soil. The dynamic stiffness matrices of the far-field region formulated in frequency domain using the present method can be easily transformed into the corresponding matrices in time domain. Hence the response can be analytical computed in time domain. Example analysis has been carried out to verify the present method for an embedded block in a multi-layered half-space. The present methods can be easily extended to the nonlinear analysis since the response analysis is carried out in time domain.

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The Rheological and Mechanical Model for Relaxation Spectra of Polydisperse Polymers

  • Kim, Nam Jeong;Kim, Eung Ryul;Hahn Sang Joon
    • Bulletin of the Korean Chemical Society
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    • v.13 no.4
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    • pp.413-419
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    • 1992
  • The theoretical equation for the relaxation spectrum of nonlinear viscoelastic polymeric material was derived from the Ree-Eyring and Maxwell non-Newtonian model. This model consists of infinite number of hyperbolic sine law Maxwell elements coupled in parallel plus a spring without a dashpot. Infinite number of nonlinear viscoelastic Maxwell elements can be used by specifying distribution of relaxation times, hole volumes, molecular weights, crystallite size and conformational size, etc. The experimentals of stress relaxation were carried out using the tensile tester with the solvent chamber. The relaxation spectra of nylon 6 filament fibers in various electrolytic solutions were obtained by applying the experimental stress relaxation curves to the theoretical equation of relaxation spectrum. The determination of relaxation spectra was performed from computer calculation.

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A Pollution Adaptive Mesh Generation Algorithm Using Singular Shape Functions (특이 형상함수를 이용한 Pollution 적응 요소생성 알고리즘)

  • 유형선;장준환;편수범
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.110-118
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    • 2001
  • In many areas of finite element analysis, elements with special properties are required to achieve maximal accuracy. As examples, we may mention infinite elements for the representation of spatial domain that extend to special and singular elements for modeling point and line singularities engendered by geomeric features such as reentrant corners and cracks. In this paper, we study on modified shape function representing singular properties and algorigthm for the pollution adaptive mesh generation. We will also show that the modified shape function reduces pollution error and local error.

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Seismic Response Analysis Method for 2-D Linear Soil-Structure Systemsusing Finite and Infinite Elements (유한요소와 무한요소를 사용한 2차원 선형 지반-구조물계의 지진응답해석법)

  • 김재민;윤정방;김두기
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.13 no.2
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    • pp.231-244
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    • 2000
  • This paper presents a dynamic analysis technique for a 2-D soil-structure interaction problem in the frequency domain, which can directly be applied as an analysis tool for seismic response analyses of underground structures, tunnels, embankments, and so on. In this method, the structure and near-field soil is modeled by the standard finite elements, while the unbounded far-field soil is represented using the dynamic infinite elements in the frequency domain. The earthquake-input motion is regarded as traveling P and SV waves which are incident vertically from the far-field of underlying half-space to the near-field of layered medium. The equivalent earthquake forces are then calculated utilizing so-called fixed-exterior-boundary-method and the free-field responses including displacements and tractions. For the verification of the present study, seismic response analyses are carried out for a multi-layered half-space free-field soil medium and a cylindrical cavity embedded in a homogeneous half-space. Comparisons of the present results with solutions by other approaches indicate that the proposed methodology gives accurate estimates. Finally, an application example of seismic response analysis for a subway station is presented, which demonstrates the applicability of the present study.

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Nonlinear interaction behaviour of infilled frame-isolated footings-soil system subjected to seismic loading

  • Agrawal, Ramakant;Hora, M.S.
    • Structural Engineering and Mechanics
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    • v.44 no.1
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    • pp.85-107
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    • 2012
  • The building frame and its foundation along with the soil on which it rests, together constitute a complete structural system. In the conventional analysis, a structure is analysed as an independent frame assuming unyielding supports and the interactive response of soil-foundation is disregarded. This kind of analysis does not provide realistic behaviour and sometimes may cause failure of the structure. Also, the conventional analysis considers infill wall as non-structural elements and ignores its interaction with the bounding frame. In fact, the infill wall provides lateral stiffness and thus plays vital role in resisting the seismic forces. Thus, it is essential to consider its effect especially in case of high rise buildings. In the present research work the building frame, infill wall, isolated column footings (open foundation) and soil mass are considered to act as a single integral compatible structural unit to predict the nonlinear interaction behaviour of the composite system under seismic forces. The coupled isoparametric finite-infinite elements have been used for modelling of the interaction system. The material of the frame, infill and column footings has been assumed to follow perfectly linear elastic relationship whereas the well known hyperbolic soil model is used to account for the nonlinearity of the soil mass.

Magnetic Field Computations of the Magnetic Circuits with Permanent Magnets by Infinite Element Method (무한요소법을 이용한 영구자석 자기회로의 자장해석)

  • 한송엽;정현규
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.34 no.10
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    • pp.379-383
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    • 1985
  • A method employing infinite elements is described for the magnetic field computations of the magnetic circuits with permanent magnet. The system stiffness matrix is derived by a variational approach, while the interfacial boundary conditions between the finite element regions and the infinite element regions are dealt with using collocation method. The proposed method is applied to a simple linear problems, and the numerical results are compared with those of the standard finite element method and the analytic solutions. It is observed that the proposed method gives more accurate results than those of the standard finite element method under the same computing efforts.

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