• Title, Summary, Keyword: 비선형 해석

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Dual-Limit Cycle Oscillation of 2D Typical Section Model considering Structural Nonlinearities (구조 비선형을 고려한 이차원 단면 날개 모델의 이중 제한 주기 운동)

  • Shin, Won-Ho;Bae, Jae-Sung;Lee, In
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.5
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    • pp.28-33
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    • 2005
  • Nonlinear aeroelastic characteristics of a two dimensional typical section model with bilinear plunge spring are investigated. Doublet-point method(DPM) is used for the calculation of supersonic unsteady aerodynamic forces which are approximated by using the minimum-state approximation. For nonlinear flutter analysis structural nonlinearity is represented by an asymmetric bilinear spring and is linearized by using the describing function method. The linear and nonlinear flutter analyses indicate that the flutter characteristics are significantly dependent on the frequency ratio. From the nonlinear flutter analysis, various types of limit cycle oscillations are observed in a wide range of air speeds below or above the linear flutter boundary. The nonlinear flutter characteristics and the nonlinear aeroelastic responses are investigated.

Effect of Simplified Methods in Seismic Analysis of Bridges (교량의 지진해석에서 단순해석의 효과)

  • Choi, Eunsoo
    • Journal of Korean Society of Steel Construction
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    • v.14 no.6
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    • pp.729-734
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    • 2002
  • The effect of several simplified methods of seismic analysis is estimated. The pounding/contacting of superstructures were considered in the multispan simply supported bridge and the multispan continuous bridge. Although nonlinear time history analysis is generally used for seismic analysis of bridges, many codes including AASHTO propose several simplified analysis methods. AASHTO, however, does not mention pounding. Therefore, the simplified methods may produce results that are different from those of nonlinear time history analysis. This study developed nonlinear analytical models of the two types of bridges mentioned. The models were then modified to the simplified linear models for simplified analysis. The results of the simplified methods were compared with those of nonlinear time history analysis. It was found that including of the pounding/contacting element in the simplified methods generated responses similar to those of the nonlinear time history analysis.

T-S Fuzzy Modeling of Nonlinear Synchronous Generator and Global Stability Analysis by Using LMI Method (비선형 동기발전기의 T-S 퍼지 모델링 및 LMI를 이용한 광역 안정도 해석)

  • Lee, Hee-Jin;Park, Jung-Wook
    • Proceedings of the KIEE Conference
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    • pp.52-53
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    • 2008
  • 전력 설비가 증대되고 복잡해짐에 따라 보다 정밀한 제어가 요구되어지고 있다. 그러나 전력시스템의 비선형성으로 인해 정확한 해석이 용이하지 않다. T-S 퍼지 모델링 기법은 시스템의 비선형성을 선형행렬 부등식을 이용하여 해석 가능하게 한다. 본 논문에서는 비선형 4차 동기발전기 모델에 T-S 퍼지 모델링 기법을 적용하여 시스템 안정도를 해석하였다.

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Direcy Design of Space Steel Frames Using practical Advanced Analysis (실용적인 고등해석을 이용한 공간 강뼈대구조물의 직접설계)

  • Kim, Seung Eock;Choi, Se Hyu
    • Journal of Korean Society of Steel Construction
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    • v.13 no.2
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    • pp.153-162
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    • 2001
  • A direct design method of three-dimensional frames using practical advanced analysis is presented. In this method. separate member capacity checks encompassed by the code specifications are not required. because the stability of separate members and the structure as a whole can be rigorously treated in determining the maximum strength of the structures. Advanced analysis accounts for geometric and material nonlinearities. The geometric nonlinearlity is considered by the use of stability function. The material nonlinearity is accounted for using CRC tangent modulus and parabolic function. The load-displacements predicted by the proposed analysis compare well with those given by other approaches. A design example has been presented for a 22-story frame. The analysis results show that the proposed method is suitable for adoption in practice.

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Nonlinear Finite Element-Boundary Element Analysis of Multi-Layered Structural Systems (유한요소와 경계요소의 조합에 의한 다층 구조계의 비선형 해석)

  • 김문겸;허택녕;이상도
    • Computational Structural Engineering
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    • v.7 no.4
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    • pp.57-67
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    • 1994
  • It is usual that underground structures are constructed within a multi-layered medium. In this paper, an efficient numerical modelling of multi-layered structural systems is studied using coupled analysis of finite elements and boundary elements. The finite elements are applied to the area in which the material nonlinearity dominates, and the boundary elements are applied to the far field where the nonlinearity is relatively weak. In the boundary element modelling of the multi-layered medium, fundamental solutions are not readily available. Thus, methods which can utilize existing Kelvin solutions are sought for the interior multi-layered domain problem. The interior domain problem which has piecewise homogeneous layers is analyzed using boundary elements with Kelvin solution, by discretizing each homogeneous subdomain and enforcing compatibility and equilibrium conditions between interfaces. Developed methodology is verified by comparing its results with those from the finite element analysis and it is concluded that coupled analysis using boundary elements and finite elements can be reasonable and efficient.

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A Study on Nonlinear GPA for Optimal Measurement Parameter Selection of Turboprop Engine (터보프롭 엔진의 최적 계측 변수 선정을 위한 비선형 GPA 기법에 관한 연구)

  • 공창덕;기자영
    • Journal of the Korean Society of Propulsion Engineers
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    • v.5 no.1
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    • pp.69-75
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    • 2001
  • Linear GPA(Gas Path Analysis) and non-linear GPA programs for performance diagnostics of a turboprop engine were developed, and a study for selection of optimal measurement variables was performed. Simultaneous faults in the compressor, the compressor turbine and the power turbine, which occur damage of the engine, were assumed. The non-linear GPA analysis was carried out with an iterative method, where the performance degradation rate of independent parameters was divided into same intervals. It was compared with the result by the Newton-Raphson method for observing the effect of an iterative method. According to the analysis result, it was found that performance of non-linear GPA can be influenced on the type of the iterative method. For showing effects of the number of measurement variables both the linear and non-linear GPAs were analyzed with 10, 8 and 6 measurement sets, respectively. RMS error between them were compared each other. It was realized that the more measurement parameters are used, and the more accurate result may be obtained. However much better result can be obtained with measurement parameters selected properly Moreover, RMS error by using non-linear GPA was less than that by using linear GPA.

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Dynamic Characteristic Analysis of a Single-phase Line Start Permanent Magnet Synchronous Motor Considering Non-linear Effects (단상 LSPM 동기전동기의 비선형 효과를 고려한 동특성해석)

  • Yu, Byoung-Hun;Kim, Byung-Taek
    • Proceedings of the KIEE Conference
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    • pp.67-69
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    • 2009
  • 본 논문에서는 자성재료의 비선형성을 고려한 단상 직입 영구자석형(LSPM) 동기전동기의 기동특성해석을 다룬다. 전동기의 운전상태에 따른 자성재료의 비선형특성을 고려하기 위해 정자장 유한요소법을 이용하여 d축과 q축에 대해 전류변화에 따른 인덕턴스를 추출하였다. 계산된 인덕턴스를 LSPM의 등가회로에 적용하였으며 Runge-Kutta 법을 이용하여 시간차분해석을 수행하였다. 제시된 해석방법으로 계산된 기동특성과 유한요소해석결과를 비교함으로써 비선형의 영향을 고찰 하였다.

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Study on Input Baseline Corretion in Nonlinear Seismic Analysis (비선형 지진해석에서 입력의 기준선 조정에 관한 연구)

  • 신태명;신응수
    • Journal of KSNVE
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    • v.10 no.2
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    • pp.338-344
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    • 2000
  • 비선형 구조물에 대하여 미끄러짐 또는 기울어짐 해석을 수행할 때에는 수평 두 방향 입력을 동시에 고려하는 해석을 수행할 것을 추천한다. 그 이유는 단일 방향 입력만을 고려한 비선형 해석의 결과가 입력지진의 기준선 조정 여부에 아주 민감하고 자칫 과도하게 보수적이거나 또는 오히려 비보수적인 결과를 초래할 수 있기 때문이다. 특히, 오래 전에 작성되어 일차적 해석만 가능한 전산 프로그램을 사용하여 해석하는 경우 주의가 요구된다. 본 논문에서는 입력지진의 기준선조정에 의한 영향을 수평 단일방향 입력만을 고려하는 해석과 수평 두 방향 입력을 동시에 고려하는 해석에 대하여 살펴본다. 이를 위하여 자립형 계에 대한 예저 헤석을 수행한 결과, 단일방향 비선형 해석시 나타날 수 있는 이러한 불확실성을 피하기 위하여 두 방향 입력을 동시에 고려하는 해석이 필요하고 입력 지진의 기준선 조정과 연계된 표준화된 지침이 필요하다는 것을 알 수 있었다.

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Design of Anchorage Zone in Prestressed Concrete Structure Using Nonlinear Strut-and-Tie Model (비선형 스트럿-타이 모델을 이용한 PSC 구조물의 정착부 설계)

  • 배한욱;송하원;변근주;변윤주
    • Magazine of the Korea Concrete Institute
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    • v.10 no.5
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    • pp.101-107
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    • 1998
  • 본 논문은 비선형 스트럿-타이 모델에 의한 프리스트레스트 콘크리트 정착부의 거동해석 및 설계에 관한 연구이다. 프리스트레스트 콘크리트 구조물의 정착부는 긴장재의 인장력 도입으로 인해 비교적 작은 단면에 큰 집중하중으로 발생하는 매우 중요한 구조부위이며, 기존의설계가 비교적 다른 구조부위의설계에 비하여 경험적으로 이루어지고 있을 뿐 만 아니라 해석에도 많은 시간과 계산량이 소요되는 단점이 있다. 비선형 스트럿-타이 모델을 대상 정착부의 비선형 재료거동을 따르도록 비선형 해석을 실시하여 설계를 수행하고 구조물의 극한하중을 추정하는 방법이다. 본 논문에서는 긴장력이 정착부의 중앙에 도입되는 경우, 편심으로 도입되는 경우, 다중 정착구가 존재하는 경우에 대하여 선형과 비선형 스트럿-타이 모델을 구성하여 정착부의 역학적 거동을 고찰하였고 실험결과와 비교하였다. 비교로부터 비선형 모델을 사용한 경우 선형 모델을 사용한 경우보다 안정성을 유지하면서 경제적인 설계가 가능하고 추정극학강도도 실험결과에 더욱 근접함을 알았다.

An efficient method for fluid/structure interaction analysis considering nonlinear structural behavior (비선형 구조 해석과 공력 해석의 효율적인 연계 알고리즘에 대한 연구)

  • Kim, Euiyoung;Chang, Seongmin;Lee, Dongho;Cho, Maenghyo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.11
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    • pp.957-962
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    • 2012
  • Fluid/structure interaction (FSI) analysis is necessary to predict the response of a system in which aerodynamic pressure causes deformation of the structure, and vice versa. In dealing with a nonlinear behavior of the structure, however, a simple iterative algorithm of aerodynamic analysis with structural analysis yields no accurate results since aerodynamic pressure need to be changed in accordance with the deformation of structures. In this study, we explore an efficient and accurate method for integrating FSI analysis into structural nonlinear systems. During the course of nonlinear structural analysis, loading conditions are periodically updated by aerodynamic analysis. The accuracy and efficiency of the method is demonstrated with a high-aspect-ratio flexible wing of Global Hawk.