• Title, Summary, Keyword: 비선형 거동

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A Comparison of Seismic Capacity for The Frames with Vertical Irregularities (수직 비정형 골조의 내진성능 비교)

  • Kwag, Jin-I;Cho, So-Hoon;Kang, Dae-Eon;Kim, Jong-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.259-262
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    • 2010
  • 최근 건물형상의 다양화로 인하여 수직부재의 불규칙성이 빈번하게 발생하면서 전통적인 보-기둥 형식의 골조에서 변형된 보와 기둥의 특징을 공유하고 있는 경사기둥의 사용빈도가 높아지고 있다. 현재 국내에서 사용하고 있는 내진설계방법은 강도에 근거를 둔 설계법으로서 구조물이 탄성상태에서 저항해야 하는 부재력에 근거하고 있다. 그러나 기준에서 규정하고 있는 또는 그 이상의 지진하중이 구조물에 가해지는 경우에 구조물은 비선형 거동을 하게 되는데 구조물이 비선형 거동을 할 때에는 탄성상태와는 다른 힘의 흐름을 나타내게 된다. 본 논문에서는 12층 철골 모멘트 골조 구조물에 대하여 횡력에 저항하는 정형화된 골조와 경사기둥을 이용한 골조의 내진성능 및 비선형 거동을 조사하였다. 그 결과 강기둥-약보로 설계된 정형화된 구조물에서는 보의 소성힌지가 계속적으로 발달하면서 구조물이 저항하는데 반하여 경사기둥을 가진 구조물은 비탄성 상태에서 경사기둥에 인접한 기둥부재로 하중이 집중되면서 정형골조에 비하여 붕괴 메카니즘이 훨씬 작은 변위에서 발생하는 것을 볼 수 있었다.

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Effects of Nonlinear Motions due to Abutment-Soil Interaction upon Seismic Responses of Multi-Span Simply Supported Bridges (비선형 교대운동이 교량구조물의 지진응답에 미치는 영향분석)

  • 김상효;마호성;이상우;경규혁
    • Journal of the Earthquake Engineering Society of Korea
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    • v.6 no.6
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    • pp.17-24
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    • 2002
  • Dynamic behaviors of a bridge system with several simple spans are evaluated to examine the effects of nonlinear abutment motions upon the seismic responses of the bridge. The idealized mechanical model for the whole bridge system is developed by adopting the multi-degree-of-freedom system, which can consider various influential components. To compare the results, both linear and nonlinear abutment-backfill models are prepared. The linear system has the constant abutment stiffness, and the nonlinear system has the nonlinear stiffness considering the abutment stiffness degradation due to the abutment-soil interaction. From simulation results, the nonlinear abutment motion is found to have an important influence upon the global bridge motions. Maximum relative distances between adjacent vibration units are found to be larger than those found from the linear system. In particular, maximum relative distances at the location with the highest possibility of unseating failure are increased up to about 30% in the nonlinear system. The effects of nonlinear behavior of an abutment on the bridge seismic behaviors are also increased as the number of span increase. Therefore, it can be concluded that the abutment-soil interaction should be considered in the seismic analysis of the bridge system.

Analytical Study for Ultimate Behavior of Steel Cable-stayed Bridges under Construction Stage (시공중 강사장교의 극한거동에 대한 해석적 연구)

  • Lee, Joo-Tak;Kim, Seung-Jun;Kim, Jong-Min;Choi, Jun-Ho;Kang, Young-Jong
    • Journal of Korean Society of Steel Construction
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    • v.23 no.6
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    • pp.691-704
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    • 2011
  • This paper presents an investigation on the ultimate behavior of steel cable-stayed bridges in the construction stage, considering various geometric nonlinearities and material nonlinearities. To numerically determine the state of cable-stayed bridges in the construction stage, initial shape analysis and construction stage analysis via backward process analysis were done sequentially. Then nonlinear analysis of the state under the construction load condition, considering the weight of the derrick crane and the key segment of the girder loaded onto the tip of the center span, was performed to investigate the ultimate behavior of the structure. The effects of the girder-mast stiffness ratio, the cable-arrangement types, and the area of the stay cables on the ultimate behavior were also extensively investigated. Moreover, the results of the ultimate analysis, considering both geometric nonlinearities and material nonlinearities, were compared with the results of the geometric nonlinear analysis, for a more meaningful investigation of the ultimate behavior of steel cable-stayed bridges in the construction stage.

A Study on the Behaviour of Nonlinear Dynamic Absorber (비선형 동흡진기의 동적거동에 관한 연구)

  • 박철희;송석홍;신현재
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.55-58
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    • 1992
  • 일반적으로 기계계 또는 기계요소가 외력을 받아 진동할 때 공진이 문제시 되는 경우가 많다. 이러한 계의 공진 제어에는 주로 댐핑재료(damping material)의 사용이 일반화 되어왔다. 그러나 댐핑재료를 사용한 제어에 있어 서는 계의 특성이나 규모등에 따라 많은 제한요소가 따르는데 특히 구조물 의 규모가 커지거나 복잡해지면, 제어 위치선정에도 어려움이 따르며 그 효 과도 기대하기 어렵다. 다른 방법으로는 기계계의 동적 특성치에 변화를 주 는 것이나, 이를 허용하지 않는 계가 많다. 따라서 이러한 단점들을 보완하 기 위해서 고안된 것이 동흡진기(dynamic absorber)이다. 기존의 선형 동흡 진기[1]는 주공진 부근영역에서 가진되는 계에만 적용이 가능하기 때문에, 흡진기와 기계계의 크기비(ratio)의 결정이 제한적이다. 이런 제한을 극복하 여 비교적 넓은 범위의 가진 주파수에 대해서 최대의 응답을 최소화하기 위 해서는 비선형 동흡진기[5]의 해석이 요구되고 있다. 제어대상의 최적응답을 얻기 위해 흡진기의 크기를 변화시키는 과정을 tuning이라 하는데, 이 과정 을 통해 최적의 감쇠값을 결정할 수 있다. 비선형 흡진기의 장점은 tuning 과정시 비선형 파라미터 변화에 의해 제어가 가능한 영역을 확장할 수 있다. 따라서 본 연구에서는 동흡진기의 tuning 과정시 흡진기의 크기비와 비선형 파라미터비에 따른 효과를 정규모우드를 활용하여 고찰한 후, 최적의 응답을 통해 비선형 동흡진기의 동적 거동을 연구하였다.

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Geometrically Non-linear Model in Flexibility Method (유연도법에서의 기하학적 비선형 모델)

  • Kwon, Min-Ho;Kim, Jin-Sup
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.63-66
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    • 2011
  • 유연도법 기반의 공식화에서는 변위영역의 형상함수를 라그랑지언(Lagrangian)보간법에 의한 곡률로부터 횡방향 변위를 유도한다. 곡률변위보간법으로 유도한 매트릭스를 사용한 기하학적 비선형 해석방법과 강성도법을 기반으로 한 비선형 기존의 유한요소 해석 프로그램의 결과를 비교하여 적용이 가능함을 확인하였고, Spacone의 이론을 확장시켜 기하학적 비선형 거동을 예측할 수 있는 유연도법의 알고리즘을 제안하였다. 예제를 통하여 실제 문제에 대한 기하학적 비선형 해석을 수행하였다.

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Nonlinear Aeroelastic Analyses of Composite Wing with Flap (플랩을 갖는 복합재 평판 날개의 비선형 공력 탄성학 해석)

  • Shin, Won-Ho;Bae, Jae-Sung;Lee, In
    • Composites Research
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    • v.20 no.1
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    • pp.8-14
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    • 2007
  • Nonlinear aeroelastic analyses of composite wing with flap are performed considering free-play and dynamic stiffness of actuator. Doublet-Hybrid method is used for the calculation of subsonic unsteady aerodynamic forces. Free-play is modeled as a bilinear spring and is linearized by using the describing function method. Dynamic stiffness is obtained from governing equation of gear system and the aeroelastic analyses were performed according to ply-angle of laminate and material. The linear and nonlinear flutter analysis results show that the flutter characteristics are significantly dependent on the free-play and dynamic stiffness. from the nonlinear flutter analysis, various types of limit cycle oscillations are observed in a range of air speeds below or above the linear divergent flutter boundary.

Coupled Nonlinear Finite Element-Boundary Element Analysis of Nuclear Waste Storage Structures Considering Infinite Boundaries (비선형 유한요소-경계요소 조합에 의한 핵폐기구조체의 무한영역해석)

  • 김문겸;허택녕
    • Computational Structural Engineering
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    • v.6 no.4
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    • pp.89-98
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    • 1993
  • As the construction of nuclear power plants are increased, nuclear wastes disposal has been faced as a serious problem. If nuclear wastes are to be buried in the underground stratum, thermo-mechanical behavior of stratum must be analyzed, because high temperature distribution has a significant effect on tunnel and surrounding stratum. In this study, in order to analyze the structural behavior of the underground which is subject to concentrated heat sources, a coupling method of nonlinear finite elements and linear boundary elements is proposed. The nonlinear finite elements (NFE) are applied in the vicinity of nuclear depository where thermo-mechanical stress is concentrated. The boundary elements are also used in infinite domain where linear behavior is expected. Using the similar method as for the problem in mechanical field, the coupled nonlinear finite element-boundary element (NFEBE) is developed. It is found that NFEBE method is more efficient than NFE which considers nonlinearity in the whole domain for the nuclear wastes depository that is expected to exhibit local nonlinearity behavior. The effect of coefficients of the rock mass such as Poisson's ratio, elastic modulus, thermal diffusivity and thermal expansion coefficient is investigated through the developed method. As a result, it is revealed that the displacements around tunnel are largely dependent on the thermal expansion coefficients.

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Analytical Study of Geometric Nonlinear Behavior of Cable-stayed Bridges (사장교의 기하학적 비선형 거동의 해석적 연구)

  • Kim, Seungjun;Lee, Kee Sei;Kim, Kyung Sik;Kang, Young Jong
    • Journal of The Korean Society of Civil Engineers
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    • v.30 no.1A
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    • pp.1-13
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    • 2010
  • This paper presents an investigation on the geometric nonlinear behavior of cable-stayed bridges using geometric nonlinear finite element analysis method. The girder and mast in cable-stayed bridges show the combined axial load and bending moment interaction due to horizontal and vertical forces of inclined cable. So these members are considered as beam-column member. In this study, the nonlinear finite element analysis method is used to resolve the geometric nonlinear behavior of cable-stayed bridges in consideration of beam-column effect, large displacement effect (known as P-${\delta}$ effect) and cable sag effect. To analyze a cable-stayed bridge model, nonlinear 6-degree of freedom frame element and nonlinear 3-degree of freedom equivalent truss element is used. To resolve the geometric nonlinear behavior for various live load cases, the initial shape analysis is performed for considering dead load before live load analysis. Then the geometric nonlinear analysis for each live load case is performed. The deformed shapes of each model, load-displacement curves of each point and load-tensile force curves for each cable are presented for quantitative study of geometric nonlinear behavior of cable-stayed bridges.

Behavior of Composite Structure by Nonlinearity of Steel - concrete Interface (I) -Parametric Study for Nonlinear Model of Interface- (강·콘크리트 경계면의 비선형성에 따른 합성구조체 거동(I) -비선형 경계면 모델에 따른 매개변수 연구-)

  • Jeong, Youn Ju;Jung, Kwang Hoe;Kim, Byung Suk
    • Journal of Korean Society of Steel Construction
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    • v.15 no.5
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    • pp.499-507
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    • 2003
  • As the load is increased on the steel-concrete composite structure, its interface begins to show nonlinear behavior due to the reduction of interaction, micro-crack, slip and separation, and it causes slip-softening, Therefore, it is essential to consider the partial-interaction analysis technique. Until now, however, full-interaction or, in some instances, the linear-elastic model, which are insufficient to simulate accurate behavior, are assumed in the analysis of composite structure since the analysis method and nonlinear model for interface are very difficult and complicated. Therefore, the design of composite structure is followed by the experimental method which is inefficient-because a number of tests have to be carried out according to the design environments. In this study, we carried out the nonlinear analysis according to various interface nonlinear models by interaction magnitude, and analyzed more accurate structural behavior and performance by maximum tangential traction and slip-softening at the interface. As a result of this study. we were able to prove that the nonlinear model of interface more exactly represents behavior after yielding, such as ultimate load: that initial tangential stiffness of interface has a significant effect on the yielding load of structural members or part: and that the maximum tangential traction and slip-softening mainly effects structural yielding and ultimate load. Therefore, the structural performance of composite structure is highly dependent on the steel-concrete interface or interaction, which may result in initial tangential stiffness, maximum tangential traction and slip-softening in nonlinear model.

Numerical Analysis for Nonlinear Static and Dynamic Responses of Floating Crane with Elastic Boom (붐(Boom)의 탄성을 고려한 해상크레인의 비선형 정적/동적 거동을 위한 수치 해석)

  • Cha, Ju-Hwan;Park, Kwang-Phil;Lee, Kyu-Yeul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.4
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    • pp.501-509
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    • 2010
  • A floating crane is a crane-mounted ship and is used to assemble or to transport heavy blocks in shipyards. In this paper, the static and dynamic response of a floating crane and a heavy block that are connected using elastic booms and wire ropes are described. The static and dynamic equations of surge, pitch, and heave for the system are derived on the basis of flexible multibody system dynamics. The equations of motion are fully coupled and highly nonlinear since they involve nonlinear mass matrices, elastic stiffness matrices, quadratic velocity vectors, and generalized external forces. A floating frame of reference and nodal coordinates are employed to model the boom as a flexible body. The nonlinear hydrostatic force, linear hydrodynamic force, wire-rope force, and mooring force are considered as the external forces. For numerical analysis, the Hilber-Hughes-Taylor method for implicit integration is used. The dynamic responses of the cargo are analyzed with respect to the results obtained by static and numerical analyses.