• Title/Summary/Keyword: Degenerated Shell

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Optimum Thickness Distributions of Plate Structure with Different Essential Boundary Conditions in the Fundamental Frequency Maximization Problem (기본고유진동수 최대화 문제에 있어서 경계조건에 따른 판구조물의 최적두께 분포)

  • Lee, Sang-Jin;Kim, Ha-Ryong
    • Proceeding of KASS Symposium
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    • 2006.05a
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    • pp.227-232
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    • 2006
  • This paper investigate the optimum thickness distribution of plate structure with different essential boundary conditions in the fundamental natural frequency maximization problem. In this study, the fundamental natural frequency is considered as the objective function to be maximized and the initial volume of structures is used as the constraint function. The computer-aided geometric design (CAGD) such as Coon's patch representation is used to represent the thickness distribution of plates. A reliable degenerated shell finite element is adopted calculate the accurate fundamental natural frequency of the plates. Robust optimization algorithms implemented in the optimizer DoT are adopted to search optimum thickness values during the optimization iteration. Finally, the optimum thickness distribution with respect to different boundary condition

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Partial Layerwise-to-ESL Coupling Elements for Multiple Model Analysis (다중모델 해석을 위한 부분층별-등가단층 결합요소)

  • Shin, Young-Sik;Woo, Kwang-Sung;Ahn, Jae-Seok
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.3
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    • pp.267-275
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    • 2009
  • This paper presents the p-convergent coupling element on the basis of the ESSE(equivalent single layer shell element) and the PLLE(partial-linear layerwise element) to analyze laminated composite plates. The ESSE is formulated by the degenerated shell theory, on the other hand, the assumption of the PLLE is piecewise linear variation of the in-plane displacement and a constant value of lateral displacement across the thickness. The proposed finite element model is based on p-convergence approach. The integrals of Legendre polynomials and Gauss-Lobatto technique are chosen to interpolate displacement fields and to implement numerical quadrature, respectively. This study has been focused on the verification of p-convergent element. For this purpose, various finite element multiple models associated with the combination of ESSE and PLLE elements are tested to show numerical stability. The simple examples such as a cantilever beam subjected vertical load and a plate with tension are adopted to evaluate the performance of proposed element.

Finite Element Analysis of Reinforced Concrete Shear Walls with a Crack under Cyclic Loading

  • Kato, S.;Ohya, M.;Shimaoka, S.;Takayama, M.
    • Computational Structural Engineering : An International Journal
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    • v.1 no.2
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    • pp.107-116
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    • 2001
  • The present paper investigates the nonlinear behavior of reinforced concrete shear walls with a crank based on a finite element analysis. The loading type is a horizontal cyclic one such as earthquake loads. Experiments of the shear walls with and without cranks, performed previously to see flow the behavior changes depending on the crank, are compared with the results obtained from the finite element analysis. The finite element analysis is based on an isoparametric degenerated shell formulation. The nonlinear constitutive equations fur concrete are modeled adopting the formulation based on a concept of Ring Typed-Lattice Model. The experiments indicate that the shear walls with a crank have low stiffness and relatively low carrying capacity compared with an ordinary plane shear wall without cranks and that they are more ductile, and the tendency is a1so confirmed based on the finite element analysis. Moreover, a good agreement between the experiments and analyses is obtained, accordingly, it is confined that the present numerical analysis scheme based on the Lattice Model is a powerful one to evaluate the behavior of reinforced concrete shear walls with cranks and without cranks.

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Postbuckling Analysis of laminated composite-stringer stiffened-Curved panels Loaded in Local compression. (국부 압축력을 받는 스트링거 보강 복합적층 만곡 판넬의 좌굴후 거동해석)

  • 김조권
    • Composites Research
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    • v.13 no.1
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    • pp.25-32
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    • 2000
  • In this paper, postbuckling behavior of laminated composite-stringer stiffened-curved panels loaded in local compression is analyzed using the finite element program developed. Postbuckling Analysis is performed in dividing the panel behavior into three basic parts. The eight node degenerated shell element is used in modelling both panel and stiffeners, and the updated Lagrangian description method based on the 2nd Piola-Kirchhoff stress tensor and the Green strain tensor is used for the nonlinear finite element formulation. The progressive failure analysis is adopted in order to grasp the failure characteristics. The postbuckling experiment of the laminated composite-stiffened-curved panel had been done to verify the finite element analysis. The buckling load and the postbuckling ultimate load are compared in parametric study.

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A Study on the Optimum Thickness Distributions of Plate Structures with Different Essential Boundary Conditions (경계조건에 따른 판 구조물의 최적두께분포에 대한 연구)

  • Lee, Sang-Jin;Kim, Ha-Ryong
    • Journal of Korean Association for Spatial Structures
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    • v.5 no.4 s.18
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    • pp.53-59
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    • 2005
  • This paper provides the results of the investigation on the optimum thickness distribution of plate structures with different essential boundary conditions. In this study, the strain energy to be minimized is considered as the objective function and the initial volume of structures is used as the constraint function. The computer-aided geometric design (CAGD) such as Coon's patch representation is used to represent the thickness distribution of plates. A reliable degenerated shell finite element is adopted to calculate the accurate strain energy level of the plates. Robust optimization algorithms provided in the optimizer DOT are adopted to search the optimum thickness values during the optimization iteration. Finally, the square plate is used to find out the optimum thickness distribution of plates according to different essential boundary condition.

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Three dimensional dynamic analysis of underground tunnels by coupling of boundary and finite elements (유한요소-경계요소 조합에 의한 터널의 3차원 동적해석)

  • 이찬우;김문겸;황학주
    • Computational Structural Engineering
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    • v.8 no.3
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    • pp.91-102
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    • 1995
  • For the wave propagation problems, the influence of time-dependent dynamic behavior must be accounted in the analysis. In this study, the dynamic analysis method which combines finite elements and boundary elements is developed for the wave propagation problem modelling the infinity of medium through 3-D boundary elements and underground structure through degenerated finite shell elements. Performing dynamic analysis of underground tunnels by the proposed coupling method of boundary and finite elements, it is found that the change of the stiffness of structures has a good effect on the response. It is also found that the consideration of the repeating effect due to moving traffic loads which is difficult with existing 2-D dynamic analysis can be possible with the 3-D analysis in time domain.

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Analysis of Mechanical Behavior for a Pultruded-Wound Hollow Rod of Unsaturated Polyester Resin(UP) with Glass Fibers (인발-와인딩에 의한 불포화수지 섬유강화 중공봉의 기계적 거동해석)

  • Kim, Zoh-Gweon;Lin, Ye
    • Composites Research
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    • v.14 no.6
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    • pp.16-23
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    • 2001
  • Analysis of mechanical behavior for a pultruded-wound hollow rod is presented. For this purpose, the pultruded-wound hollow rod is manufactured by the new winder attached to the conventional pultrusion system. And the conventional pultrusion process is newly altered to manufacture pultruded-wound specimens. A computer program, POST II, is modified to perform this study, In the nonlinear finite element formulation, the updated Lagrangian description method based on the second Piolar-Kirchhoff stress tensor and the Green strain tensor are used. For the finite element modeling of the composite hollow rod, the eight-node degenerated shell element is utilized. In order to estimate the failure, the maximum stress criterion is adopted to the averaged stress in the each layer of the finite elements. As numerical examples, the behavior of glass/up composite hollow rod is investigated from the initial loading to the final collapse. Present finite element results considering stiffness degradation and stress unload due to failure shows excellent agreement with experiments in the ultimate load, failure and deformations.

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A Scanning Electron Microscopic Study of the Glochidial Encystment on the Host Fish (2) (Glochidium larva의 부착으로 인한 숙주어류의 피양형성과정에 관한 주사전자현미경적 연구 (2))

  • Jeong, Kye-Heon;Oh, Young-Sook
    • The Korean Journal of Malacology
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    • v.7 no.1
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    • pp.76-86
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    • 1991
  • A scanning electron microscopic stuey on the glochidial encystment study on the golchidal encystment and excystment of Anodonta fukudai on Acheilognathus yamatsutae, a common natural hostfish, was conducted. The glochidium easily attached to the unscaled surfaces of the host fish such as the fins, lips, and the wall of the buccal cavity. For this study, the fins infected with the glochidia wer mainly observed in a series. The process of encystment was slowly progressed, for 21-25 hours for the early cyst and for 2-4 days for the thick walled cyst. The process of excystmint was visually detected on the 12th day since the attachmint was occurred. The first visible sign was a little tear of the cyst wall covering the hinge and marginal zones of the juvenile clam and once the little sign was appeared the progress of emerging and dettachmint of the juvenile clam from the host was finished relatively in short time. During the process of the encystmint, the cells participationg in covering the attached glochidirm were seened mainly supplied by migration from the surroundings. the shapes of the cells migrating and covering the glochidium were considerably changed and the surface structures of the cells lost their normal pattern of the surface ridges. The unstable forms of the cells were observed almost all throughout the period of the glochidial attachment. No cells of the host epithelium, which were still attached to the juvenile clam energing from the cyst, were observed. The most juvenile clams escaped from the cysts were a little bigger than the glochidia and they were still possessed of the golchidial hooks even though much degenerated. The first growth line was appeared on the shell valves of the juvenild clam when observed right after dettachment.

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Realtime Simulation of Deformation due to Line Heating for Automatic Hull Forming System (곡가공 자동화 시스템을 위한 선상가열에 의한 변형의 실시간 시뮬레이션)

  • Dae-Eun Ko;Chang-Doo Jang;Seung-Il Seo;Hae-Woo Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.4
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    • pp.116-127
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    • 1999
  • Line heating is a method widely used in forming ship hull surface. From the viewpoint of mechanics it is large deformation thermal elasto-plastic problem of arbitrary shaped plate. Many researches have been carried out to resolve this problem. Especially, Jang et al.[1] proposed a simplified thermal elasto-plastic analysis method to predict effectively the deformation of plate due to line heating. In this paper, we improved the method of Jang et al.[1] by considering tension yielding in temperature decreasing stage and verified with experimental results. FEA program using MITC4 degenerated shell element was made to deal with elastic large deformation problem. The newly proposed method can be used in the simulation and control of forming hull surface for higher productivity with simplicity and efficiency.

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Changes in Protease and Formonitrogen of Salted Fish and Shellfish (1) (젓갈 성숙과정(成熟過程)에 있어 Protease 및 Formonitrogen의 변화(變化)에 관(關)한 연구(硏究)(1))

  • Suh, Myung-Jah
    • Journal of Nutrition and Health
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    • v.6 no.2
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    • pp.45-56
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    • 1973
  • Salted fish and shellfish have been widely used in Korea from olden times as side-dishes, although the processes and methods of pickling have varied depending on localities. The common raw materials for these subsidiary food articles include anchovy, shrimp, yellow corvina, oysters, octopus, top-shell, shellfish, pollack roe and pollack intestines. It must be pointed out here, however, that the salted stuffs now marketed locally are highly unscientific and unsanitary in the way they are processed and sold, and this has prompted this writer to undertake a study on these native food articles. The following findings have been obtained from this study on the changes in Formonitrogen and Protease Activity, effected by the density of salt and the degree of storing temperature, of the pickles of cedfish gills, codfish intestines, pollack intestines, shellfish, oysters, cuttle fish and octopus. 1) Codfish Gills The Protease Activity of the pickled codfish gills was greater in the groups of lesser doses of salt and higher degrees of storing temperature. The same was true in the case of Formonifrogen, too. The Formonitrogen of the pickled codfish gills was larger in the groups of lesser salt and higher teimperature. 2) Codfish Intestines The amount of Formonitrogen of the pickled codfiah intestines became greater, as time went by, in the groups of lesser salt than those of larger doses of salt, with the speed of its formation getting faster as the storing temperature rose from $5^{\circ}C$ to $15^{\circ}C$ and $30^{\circ}C$. The Protease Activity was also greater in the groups of lesser salt and higher temperature. The group, stored at 10% salt and $30^{\circ}C$, rotted in five days. 3) Pollack Intestines The amount of Formonitrogen of the pickled pollack intestines was greater in the groups of lesser amount of salt and higher degrees of storing temperature. The Protease Activity of the pickled pollack intestines began decreasing from the 11th day after the pickling in the groups stored at colmparatively high degrees of temperature$(15^{\circ}C-30^{\circ}C)$, while that of the group stored at $5^{\circ}C$ kept rising. The effects of the amount of salt were little. The group stored at 15% salt and $30^{\circ}C$ started rotting on the 13th day while that stored at $30^{\circ}C$ decayed on the 7th day. The group stored at 20% salt and $30^{\circ}C$ rotted on the 9th day. 4) Oysters The amount of Formonitrogen of the pickled oysters became greater as the storing temperature rose and the doses of salt were lowered. The Protease Activity was not affected at any measurable degree by the density of salt in the group stored at $5^{\circ}C$, but became greater as the storing temperature rose to $15^{\circ}C$ and $30^{\circ}C$. The group stored at 10% salt and $30^{\circ}C$ rotted on the 5th day while that stored at 20% salt and $30^{\circ}C$ on the 13th day. 5) Shellfish The amount of Formonitrogen of the pickled shellfish became greater, as time went by, it the groups of lower consistency of salt than the groups of higher density of salt, although the decay of the former groups was faster than the latter groups. The density of salt best fitted for the pickling appeared to be about 20% with the storing temperature to be $15^{\circ}C$, at which the pickled stuff became most tasty on the 7th day. The oysters stored in three groups at $5^{\circ}C$, $15^{\circ}C$ and $30^{\circ}C$ respectively showed the greatest Protease Activity alike at 0% of salt, but the activity declined as the density of salt increased. The Protease Activity of each group rose for the first 11 days after the pickling, but began declining from the 13th day onward, with the groups of higher temperature retaining higher Protease Activity than the groups of lower temperature. 6) Cuttlefish Both the amount of Formonitrogen and the degree of Protease Activity of the pickled cuttlefish were greater in the groups of lower density of salt and higher degree of storing temperature. The oysters pickled at 10% salt and $15^{\circ}C$ degenerated on the 13th day while that of 10% salt and $30^{\circ}C$ deteriorated on the 7th day. 7) Octopus Both the Formonitrogen and the Protease Activity of the pickled octopus were greater in the groups of lower density of salt, but as time went by, the Protease Activity in all groups dwindled after a climbing. In general, the Formonitrogen and the Protease Activity of the pickled oysters became greater as the storing temperature got higher. One group stored at 10% salt and $15^{\circ}C$ rotted in 13days while another group stored at $30^{\circ}C$ decayed in 7 days.

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