• Title/Summary/Keyword: mixed finite elements

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3-D Axisymmetric Fluid-Structure-Soil Interaction Analysis Using Mixed-Fluid-Element and Infinite-Element (혼합형 유체요소와 무한요소를 이용한 3차원 축대칭 유체-구조물-지반 상호작용해석)

  • 김재민;장수혁;윤정방
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1999.10a
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    • pp.257-266
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    • 1999
  • This paper presents a method of seismic analysis for a cylindrical liquid storage structure on/in horizontally layered half.space considering the effects of the interior fluid and exterior soil medium in the frequency domain. To capture the essence of fluid-structure-soil interaction effects effectively, a mixed finite element with two-field (u, p) approximation is employed to model the compressive inviscid fluid, while the structure and soil medium are presented by the 3-D axisymmetric finite elements and dynamic infinite elements. The present FE-based method can be applied to the system with complex geometry of fluid region as well as with inhomogeneous near-field soil medium, since it can directly model both the fluid and the soil. For the purpose of verification, dominant peak frequencies in transfer functions for horizontal motions of cylindrical fluid storage tanks with rigid massless foundation on a homogeneous viscoelastic half.space are compared with those by two different added mass approaches for the fluid motion. The comparison indicates that the Present FE-based methodology gives accurate solution for the fluid-structure-soil interaction problem. Finally, as a demonstration of versatility of the present study, a seismic analysis for a real-scale LNG storage tank embedded in layered half.space is carried out, and its member forces along the height of the structure are compared with those by an added mass approach developed by the present writers.

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A Study on the Criterion for Membrane/Shell Mixed Element and Analysis of Sheet Metal Forming Problem (박막/쉘 혼합요소를 이용한 박판성형 해석과 박막/쉘 판별조건에 관한 연구)

  • Jeong, Dong-Won;Yang, Gyeong-Bu
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.57-64
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    • 1998
  • This study is concerned with criterion for membrane to shell conversion in two-dimensional elastic-plastic finite element analysis using membrane/shell mixed element. It is well known that in the sheet metal forming some parts of the sheet deform under almost pure stretching (membrane) conditions, whereas other parts in contact with sharp tooling surfaces can develop significant bending strains. The membrane analysis has a short computational time however, in the membrane analysis the bending effects can not be condidered at all. On the other hand, the shell analysis allows the consideration of bending effects, but involves too much computational time. So Onatel),2), Yang et al3),4) developed the membrane/shell mixed element. Onate introduced the energy ratio parameter and Yang et al introduced the ratio of thickness to radius of curvature as the criterion. In the present study we propose a new criterion by using the angle between both side elements in the nodal point.

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FORMULATION OF SHELL RINITE ELEMENTS BASED ON A NEW METHOD OF ELEMENT DECOMPISITION (새로운 요소분해방법에 의한 쉘 유한요소의 개발)

  • 이재영
    • Computational Structural Engineering
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    • v.1 no.1
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    • pp.67-78
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    • 1988
  • A new method of element decomposition is suggested for simple, efficient, and generalized formulation of shell finite elements. The kernel of the method is to decompose conceptually the actual element into a translational element and a difference element. The actual element is obtained by combining the two component elements. The derived element can be classified into three basic types depending on how the element is decomposed. A few complementary measures, to remove locking phenomena and thus improve the performance of the elements, have been studied. They are reduced integration, addition of internal degrees of freedom, and mixed formulation. A rational method of controlling spurious zero energy modes has also been devised. Validity and efficiency of the element with or without complementary measures have been examined through a series of numerical studies.

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An Analytical Approach for Structural Synthesis of Substructures

  • Eun, Hee-Chang;Park, Sang-Yeol;Lee, Eun-Taik
    • Journal of Mechanical Science and Technology
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    • v.18 no.9
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    • pp.1529-1536
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    • 2004
  • A structure is broken down into a number of substructures by means of the finite element method and the substructures are synthesized for the complete structure. The divided substructures take two types: fixed-free and free-free elements. The flexibility and stiffness matrices of the free-free elements are the Moore-Penrose inverse of each other. Thus, it is not easy to determine the equilibrium equations of the complete structure composed of two mixed types of substructures. This study provides the general form of equilibrium equation of the entire structure through the process of assembling the equilibrium equations of substructures with end conditions of mixed types. Applications demonstrate that the proposed method is effective in the structural analysis of geometrically complicated structures.

Mixed Mode Crack Propagation Models of the Concrete Beams (콘크리트 보에서의 혼합모드 균열전파에 관한 연구)

  • 이상석
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1999.04a
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    • pp.256-266
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    • 1999
  • The angled crack which is the simplest and representative case in the mixed mode crack analysis has stimulated the interests of many investigators during past 20 years. In this study the conventional quadratic isoparametric elements were used in all regions except the crack tip zone where triangular singularity elements with 6 nodes were used. The stress intensity factor of K1 and KII were determined respectively by the displacement correlation method. The finite element analysis program in this paper based on maximum energy release rate criteria and the results obtaiend by this program were compared with those calculated from the maximum circumferential tensile criteria and those by Jenq and Shah's experiments of the same geometry and material properties

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An interface element for modelling the onset and growth of mixed-mode cracking in aluminium and fibre metal laminates

  • Hashagen, Frank;de Borst, Rene
    • Structural Engineering and Mechanics
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    • v.5 no.6
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    • pp.817-837
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    • 1997
  • In the present contribution an interface crack model is introduced which is capable of modelling crack initialisation and growth in aluminium as well as in Fibre Metal Laminates. Interface elements are inserted in a finite element mesh with a yield function which bounds all states of stress in the interface. Hardening occurs after a state of stress exceeds the yield stress of the material. The hardening branch is bounded by the ultimate stress of the material. Thereafter, the state of stress is reduced to zero while the inelastic deformations grow. The energy dissipated by the inelastic deformations in this process equals the fracture energy of the material. The model is applied to calculate the onset and growth of cracking in centre cracked plates made of aluminium and GLARE$^{(R)}$. The impact of the model parameters on the performance of the crack model is studied by comparisons of the numerical results with experimental data.

3D nonlinear mixed finite-element analysis of RC beams and plates with and without FRP reinforcement

  • Hoque, M.;Rattanawangcharoen, N.;Shah, A.H.;Desai, Y.M.
    • Computers and Concrete
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    • v.4 no.2
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    • pp.135-156
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    • 2007
  • Three 3D nonlinear finite-element models are developed to study the behavior of concrete beams and plates with and without external reinforcement by fibre-reinforced plastic (FRP). All three models are formulated based upon the 3D theory of elasticity. The stress model is modified from the element developed by Ramtekkar, et al. (2002) to incorporate material nonlinearity in the formulation. Both transverse stress and displacement components are used as nodal degrees-of-freedom to ensure the continuity of both stress and displacement components between the elements. The displacement model uses only displacement components as nodal degrees-of-freedom. The transition model has both stress and displacement components as nodal degrees-of-freedom on one surface, and only displacement components as nodal degrees-of-freedom on the opposite surface. The transition model serves as a connector between the stress and the displacement models. The developed models are validated by comparing the results of the analyses with an existing experimental result. Parametric studies of the effects of the externally reinforced FRP on the load capacity of reinforced concrete (RC) beams and concrete plates are performed to demonstrate the practicality and the efficiency of the proposed models.

MINIMAL LOCALLY STABILIZED Q1-Q0 SCHEMES FOR THE GENERALIZED STOKES PROBLEM

  • Chibani, Alima;Kechkar, Nasserdine
    • Journal of the Korean Mathematical Society
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    • v.57 no.5
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    • pp.1239-1266
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    • 2020
  • In this paper, some novel discrete formulations for stabilizing the mixed finite element method Q1-Q0 (bilinear velocity and constant pressure approximations) are introduced and discussed for the generalized Stokes problem. These are based on stabilizing discontinuous pressure approximations via local jump operators. The developing idea consists in a reduction of terms in the local jump formulation, introduced earlier, in such a way that stability and convergence properties are preserved. The computer implementation aspects and numerical evaluation of these stabilized discrete formulations are also considered. For illustrating the numerical performance of the proposed approaches and comparing the three versions of the local jump methods alongside with the global jump setting, some obtained results for two test generalized Stokes problems are presented. Numerical tests confirm the stability and accuracy characteristics of the resulting approximations.

Nonlinear Behaviors of Mixed Structure Considering Advanced Connection Types (개선된 접합부 방식을 갖는 혼합구조의 비선형 거동)

  • Huh, Taik-Nyung;Yun, Ik-Jung;Kim, Mun-Kyum;Cho, Sung-Yong;Shim, Byul
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.677-682
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    • 2007
  • Nonlinear analysis of mixed structures is carried out by utilizing contact elements of a general finite element analysis computer program(ABAQUS). The present analysis focuses on the enhancing behaviors of mixed structure's connection type. Main 2 issues are related with discontinuity which reduce the stiffness of structure and proposing enhanced connection type. To validate the present study approaching 2 way, analytic one and experimental test.

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Finite Element Mesh Generation from 3D Laser Scanned Data (3차원 레이저 스캐닝 점 좌표 데이터로부터 CAE 유한 요소 메쉬 생성 알고리즘 개발)

  • Jarng S.S.;Yang H.J.;Lee J.H.
    • Korean Journal of Computational Design and Engineering
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    • v.10 no.1
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    • pp.70-75
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    • 2005
  • A 3D solid element mesh generation algorithm was newly developed. 3D surface points of global rectangular coordinates were supplied by a 3D laser scanner. The algorithm is strait forward and simple but it generates mixed solid elements such as hexagonal, pyramid and prism types. Then, the surface triangular or rectangular elements were generated from the solid elements. The key of the algorithm is elimination of elements and 3D adaptive surface smoothing using given 3D surface point data.