• Title/Summary/Keyword: Critical Load

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Influential Parameters on Offshore Jacket Structure Launching (해양 자켓구조물 진수 영향인자에 대한 고찰)

  • 조철희;김경수;김재환;이수훈
    • Journal of Ocean Engineering and Technology
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    • v.15 no.2
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    • pp.141-147
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    • 2001
  • The launching process is one of the most critical operations for large structure in offshore installation. Since as the size increases it limits the availability of offshore crane facilities, the large jacket structures are often installed by launching. As the structure approaches to tilt beam, it reaches critical load, and there are parameters to affect on launching procedure. The major influential parameters are trim, draft of barge, center of gravity, center of buoyancy and reserved buoyancy of jacket. As increasing of trim and draft, structural loads tend to decrease. The trim is found to be more contributing than draft on structural loads. Therefore the trim should be increased so as to decrease structural loads and to avoid stalling of structure and submergence of stern. During the launching process, the distance between jacket and seabed should be investigated which differs from the amount of reserved buoyancy and launching condition of barge. In this paper the effects of parameters on launching process are numerically investigated.

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Analysis on Voltage Compensating Effect of DVR using PSCAD/EMTDC (PSCAD/EMTDC를 이용한 DVR의 전압보상 효과분석)

  • Park, Sang-Ho;Choy, Young-Do;Park, Young-Shin
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.9
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    • pp.165-171
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    • 2010
  • There are many researches on Power Quality Device to protect the critical load and power system as the nonlinear load and precision load are adopted into the power system recently. To analyze the voltage compensation of voltage sag and voltage swell by DVR, which is connected to the important load in series, this paper shows PSCAD/EMTDC simulation and its verification by comparing with the actual DVR output of 2MVA. DVR control scheme in this paper is applicable to compensate single-phase, 2-phases or 3-phases voltage sag as well as DVR for distribution system.

Customer's Effects of Momentary Voltage Sag in Power Distribution System Considering Reclosing Interval (리클로징 시간을 고려한 배전계통 순간전압강하의 수용가측 영향)

  • Moon, Jong-Fil;Kim, Jae-Chul;Kang, Bong-Seok;Yun, Sang-Yun
    • Proceedings of the KIEE Conference
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    • pp.36-38
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    • 2003
  • In this paper, It was evaluated that the customer's effects of momentary voltage sag in power distribution system considering reclosing interval. Above all, power quality problems were discussed widely, various international standards about power quality were compared to each other. after the continuous voltage sag waves of power distribution system on fault were induced, the experimentation about voltage sag for critical load was performed using source simulator. The results of experimentation were displayed as the form of 2 and 3-dimensional CBEMA Curve.

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The Elastic Critical Loads of Linearly Non-symmetrically Tapered Members (직선형으로 Taper진 비대칭 변단면 부재의 탄성임계하중)

  • 김효중;홍종국;이수곤
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.299-306
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    • 2000
  • The elastic critical load of a slender compression member plays an important role when the proper design of that member is required. For tapered compression members, however, there are cases when the conventional neutral equilibrium or energy method can't be applied to the determination of critical loads. In this paper, the finite element method is applied to the approximate determination of the linearly tapered members. In this paper, the bars are assumed to be tapered linearly along their axes. The parameters considered in this study are taper parameter, α and the sectional property parameter, m. The member ends are either hinged or fixed. The computed results using the finite element method are represented in the forms of algebraic equations. The regression technique is employed to determine the coefficients of the algebraic equations. Critical loads estimated by the proposed algebraic equations coincide flirty well with those employing the finite element method.

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Effective Length Factors of Framed Columns with Sinusoidally Tapered Sections (정현상 변단면 기둥의 유효길이 계수)

  • 박재영;송상용;김순철;이수곤
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.243-250
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    • 2003
  • A method for the determination of effective length factors of the framed columns with sinusoidally tapered sections is proposed. In the study, the stability analysis of the single story-two equal bay, frame with tapered columns is performed first by finite element method. The changes of the critical load coefficients of frames are reprersented by algebraic equations of the analysis parameters. The effective length factor formula is expressed in terms of proposed algebraic equation. The effective length factors for the prismatic columns (α=0.0) estimated by the proposed method coincide fairly well with those determined by the analytical method.

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Nonlinear dynamic buckling of laminated angle-ply composite spherical caps

  • Gupta, S.S.;Patel, B.P.;Ganapathi, M.
    • Structural Engineering and Mechanics
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    • v.15 no.4
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    • pp.463-476
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    • 2003
  • This paper deals with nonlinear asymmetric dynamic buckling of clamped laminated angle-ply composite spherical shells under suddenly applied pressure loads. The formulation is based on first-order shear deformation theory and Lagrange's equation of motion. The nonlinearity due to finite deformation of the shell considering von Karman's assumptions is included in the formulation. The buckling loads are obtained through dynamic response history using Newmark's numerical integration scheme coupled with a Newton-Raphson iteration technique. An axisymmetric curved shell element is used to investigate the dynamic characteristics of the spherical caps. The pressure value beyond which the maximum average displacement response shows significant growth rate in the time history of the shell structure is considered as critical dynamic load. Detailed numerical results are presented to highlight the influence of ply-angle, shell geometric parameter and asymmetric mode on the critical load of spherical caps.

A Safety Analysis on the Structural Rupture of Cylindrical Shell by Finite Difference Method (차분법에 의한 실린더형 쉘구조의 안정성 연구)

  • Kim, Chi-Kyung;Park, Hwa-Yong
    • Journal of the Korea Safety Management & Science
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    • v.13 no.3
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    • pp.37-43
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    • 2011
  • 본 연구에서는 실린더 형 쉘 구조물의 구조적 안정성에 대하여 해석 하였다. 임계하중은 하중을 점차적으로 증가 하여 구조물이 파괴가 발생 할 때의 상태에서 가장 작은 하중을 의미한다. 셀 구조의 안정성을 임계하중의 크기로 기초를 두고 해석 하였다. 실린더 형 쉘의 차분해석은 일차적 원통형 판구조와 같으므로 최근에 많은 연구의 대상이 되어왔다. 차분법은 복잡한 구조물에서도 물론, 다양한 경계조건을 포함하는 문제에 이르기까지 효과적인 수치방법이다. 본 연구에서는 기본 쉘의 지배방정식을 유도하고 차분화 하여 직접적으로 접근하였다. 등분포 하중의 내압을 받고 있는 갇힌 실린더 형 쉘의 처짐 및 응력을 해석 하였다. 수치해석 결과를 해석해와 비교 검토하였으며 안정성에 대하여 임계 하중강도의 범위를 산출하였다.

Elastic Critical Loads of Tapered Compression Members with Simply Supported Ends (단순지지 변단면 압축재의 임계하중)

  • Song, Chang-Young
    • Journal of Korean Association for Spatial Structures
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    • v.7 no.5
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    • pp.83-87
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    • 2007
  • Elastic critical loads of sinusoidally tapered bars with simply supported ends are determined by finite element method. The parameters considered in the analysis are taper parameter (=a) and section property parameter (=m). The analysis result for the special case of porismatic bar (a=0) shows good agreement with the existing value. The changes of the critical load coefficients are expressed by an algebraic equation. The coefficients appearing in the equations are determined by regression technique. The critical loads coefficients estimated by the proposed equations reveal little errors when they are compared with those determined by finite element method.

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Bending and buckling of a rectangular porous plate

  • Magnucki, K.;Malinowski, M.;Kasprzak, J.
    • Steel and Composite Structures
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    • v.6 no.4
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    • pp.319-333
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    • 2006
  • A rectangular plate made of a porous material is the subject of the work. Its mechanical properties vary continuously on the thickness of a plate. A mathematical model of this plate, which bases on nonlinear displacement functions taking into account shearing deformations, is presented. The assumed displacement field, linear geometrical and physical relationships permit to describe the total potential energy of a plate. Using the principle of stationarity of the total potential energy the set of five equilibrium equations for transversely and in-plane loaded plates is obtained. The derived equations are used for solving a problem of a bending simply supported plate loaded with transverse pressure. Moreover, the critical load of a bi-axially in-plane compressed plate is found. In both cases influence of parameters on obtained solutions such as a porosity coefficient or thickness ratio is analysed. In order to compare analytical results a finite element model of a porous plate is built using system ANSYS. Obtained numerical results are in agreement with analytical ones.

Large deflection of simple variable-arc-length beam subjected to a point load

  • Chucheepsakul, S.;Thepphitak, G.;Wang, C.M.
    • Structural Engineering and Mechanics
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    • v.4 no.1
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    • pp.49-59
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    • 1996
  • This paper considers large deflection problem of a simply supported beam with variable are length subjected to a point load. The beam has one of its ends hinged and at a fixed distance from this end propped by a frictionless support over which the beam can slide freely. This highly nonlinear flexural problem is solved by elliptic-integral method and shooting-optimization technique, thereby providing independent checks on the new solutions. Because the beam can slide freely over the frictionless support, there is a maximum or critical load which the beam can carry and it is dependent on the position of the load. Interestingly, two possible equilibrium configurations can be obtained for a given load magnitude which is less than the critical value. The maximum arc-length was found to be equal to about 2.19 times the fixed distance between the supports and this value is independent of the load position.