• Title/Summary/Keyword: dynamic relaxation method

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Numerical Study on Estimation of Static Configuration of Steel Lazy Wave Riser Using Dynamic Relaxation Method (동적이완법을 이용한 Steel Lazy Wave Riser의 정적형상 추정에 관한 수치해석적 연구)

  • Oh, Seunghoon;Jung, Jae-Hwan;Park, Byeongwon;Kwon, Yong-Ju;Jung, Dongho
    • Journal of Ocean Engineering and Technology
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    • v.32 no.6
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    • pp.466-473
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    • 2018
  • This paper presents an estimation method for the static configuration of a steel lazy wave riser (SLWR) using the dynamic relaxation method applied to estimate the configuration of structures with strong geometric non-linearity. The lumped mass model is introduced to reflect the flexible structural characteristics of the riser. In the lumped mass model, the tensions, shear forces, buoyancy, self-weights, and seabed reaction forces at nodal points are considered in order to find the static configuration of the SLWR. The dynamic relaxation method using a viscous damping formulation is applied to the static configuration analysis. Fictitious masses are defined at nodal points using the sum of the largest direct stiffness values of nodal points to ensure the numerical stability. Various case studies were performed according to the bending stiffness and size of the buoyancy module using the dynamic relaxation method. OrcaFlex was employed to validate the accuracy of the developed numerical method.

Comparison of viscous and kinetic dynamic relaxation methods in form-finding of membrane structures

  • Labbafi, S. Fatemeh;Sarafrazi, S. Reza;Kang, Thomas H.K.
    • Advances in Computational Design
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    • v.2 no.1
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    • pp.71-87
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    • 2017
  • This study focuses on the efficiency and applicability of dynamic relaxation methods in form-finding of membrane structures. Membrane structures have large deformations that require complex nonlinear analysis. The first step of analysis of these structures is the form-finding process including a geometrically nonlinear analysis. Several numerical methods for form-finding have been introduced such as the dynamic relaxation, force density method, particle spring systems and the updated reference strategy. In the present study, dynamic relaxation method (DRM) is investigated. The dynamic relaxation method is an iterative process that is used for the static equilibrium analysis of geometrically nonlinear problems. Five different examples are used in this paper. To achieve the grading of the different dynamic relaxation methods in form-finding of membrane structures, a performance index is introduced. The results indicate that viscous damping methods show better performance than kinetic damping in finding the shapes of membrane structures.

A Study of Shape Finding of Equally Stressed Surface for Membrane Structures by Dynamic Relaxation Method (동적이완법에 의한 막구조의 등장력곡면 형태해석에 관한 연구)

  • 한상을;이경수
    • Computational Structural Engineering
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    • v.11 no.4
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    • pp.321-330
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    • 1998
  • 막구조의 초기형상을 결정하기 위하여 막요소의 기하학적 비선형을 고려한 평형방정식을 유도하고, 등장력곡면(equally stressed surface)을 결정하기 위한 알고리즘을 정식화한다. 막구조는 대변형에 의한 기하학적 비선형성을 포함하고, 막구조의 특성상 초기장력에 의한 초기변형을 고려해야 하므로, 본 논문에서는 막구조와 같은 인장구조물의 비선형 수치해석을 수행하기 위한 해석기법으로써, 동적이완법(Dynamic Relaxation Method)에 대한 해석알고리즘을 적용하고, 이 방법에 의해 수행한 해석결과를 검토함으로써 막구조 해석에 적용 가능한 수치해석기법을 제시하고, 수치해석에 대한 예를 통해 본 해석법의 타당성을 검증한다.

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Geodesic shape finding of membrane structure with geodesic string by the dynamic relaxation method

  • Lee, K.S.;Han, S.E.
    • Structural Engineering and Mechanics
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    • v.39 no.1
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    • pp.93-113
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    • 2011
  • The explicit nonlinear dynamic relaxation method (DRM) is applied to the nonlinear geodesic shape finding analysis by introducing fictional tensioned 'strings' along the desired seams with a three or four-node membrane element. A number of results from the numerical example for the nonlinear geodesic shape finding and patterning analysis are obtained by the proposed method to demonstrate the accuracy and efficiency of the developed method. Therefore, the proposed geodesic shape finding algorithm may improve the applicability of a four-node membrane element to membrane structural engineering and design analysis simultaneously for the shape finding, stress, and patterning analysis.

A Study on the Post-Buckling analysis of spatial structures by using dynamic relaxation method (동적이완법을 이용한 공간구조의 후좌굴 해석에 관한 연구)

  • Lee, Kyong-Soo;Lee, Sang-Ju;Lee, Hyong-Hoon;Han, Sang-Eul
    • Proceeding of KASS Symposium
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    • pp.154-160
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    • 2005
  • The present study is concerned with the application of dynamic relaxation method in the investigation of the large deflection behavior of spatial structures. The dynamic relaxation do not require the computation or formulation of any tangent stiffness matrix. The convergence to the solution is achieved by using only vectorial quantities and no stiffness matrix is required in its overall assembled form. In an effort to evaluate the merits of the methods, extensive numerical studies were carried out on a number of selected structural systems. The advantages of using dynamic relaxation methods, in tracing the post-buckling behavior of spatial structures, are demonstrated.

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A Study on the Post-Buckling Analysis of Spatial Structures Using Dynamic Relaxation Method (동적이완법을 이용한 후좌굴 해석법의 Hybrid 구조물의 적용성 평가)

  • Lee, Kyong-Soo;Lee, Sang-Ju;Han, Sang-Eul
    • Proceeding of KASS Symposium
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    • pp.58-65
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    • 2006
  • The present study is concerned with the application of dynamic relaxation method in the investigation of the large deflection behavior of spatial structures. The dynamic relaxation do not require the computation or formulation of any tangent stiffness matrix. The convergence to the solution is achieved by using only vectorial quantities and no stiffness matrix is required in its overall assembled form. In an effort to evaluate the merits of the methods, extensive numerical studies were carried out on a number of selected structural systems. The advantages of using dynamic relaxation methods, in tracing the post-buckling behavior of spatial structures, are demonstrated.

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A Study on the Post-Buckling Analysis of Spatial Structures by using Dynamic Relaxation Method (동적이완법을 이용한 공간구조의 후좌굴 해석에 관한 연구)

  • Lee Kyong-Soo;Lee Sang-Ju;Lee Hyong-Hoon;Han Sang-Eul
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.175-182
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    • 2005
  • The present study is concerned with the application of dynamic relaxation method in the investigation of the large deflection behavior of spatial structures. This numerical algorithm do not require the computation or formulation of any tangent stiffness matrix. The convergence to the solution is achieved by using only vectorial quantities and no stiffness matrix is required in its overall assembled form. In an effort to evaluate the merits of the methods, extensive numerical studies were carried out on a number of selected structural systems. The advantages of using dynamic relaxation methods, in tracing the post-buckling behavior of spatial structures, are demonstrated.

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Shape Finding of Cable-Net Structures by Using Modified Dynamic Relaxation Method (변형된 동적이완법을 이용한 케이블-네트 구조물의 형상해석)

  • 하창우;김재열;권택진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.51-58
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    • 2000
  • Dynamic relaxation method is a shape finding analysis method for flexible structures by introducing the dynamic equilibrium equation. However, it is difficult for shape finding to estimate the most appropriate values for the mass and damping on each shape because the values are random one. In this study, the unit mass, the unit damping and the principal direction stiffness are utilized to avoid the random values, and the Newmarks assumption is introduced during the dynamic analysis. By introducing variant time increment method presented, the convergence time is reduced, that is, it can be reduced the total times for analysis.

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A study on the non-linear analysis of the elastic catenary cable considering kinetic damping (동적감쇠를 고려한 탄성 현수선 케이블의 비선형 해석에 관한 연구)

  • 한상을;정명채;이진섭
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.331-338
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    • 2000
  • In this paper, a non-linear finite element formulation for the spatial cable-net structures is simulated and using this formulation, the characteristics of structural behaviors for the elastic catenary cable are examined In the simulating procedure for the elastic catenary cable, nodal forces and tangential stiffness matrices are derived using catenary parameters of the exact solutions by a governing differential equation of catenary cable, cable self-weights and unstressed cable length. Dynamic Relaxation Method that considers kinetic damping is used for the structure analysis and Newton Raphson Method is used to verify the accuracy of solutions. In the analysis of two dimensional cable, the results obtain from the elastic catenary elements are shown more accurate than does of truss elements and in the case of spatial cable-net structures, Dynamic Relaxation Method is more stable to be converged than Newton Raphson Method.

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Nonlinear dynamic analysis by Dynamic Relaxation method

  • Rezaiee-Pajand, M.;Alamatian, J.
    • Structural Engineering and Mechanics
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    • v.28 no.5
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    • pp.549-570
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    • 2008
  • Numerical integration is an efficient approach for nonlinear dynamic analysis. In this paper, general category of the implicit integration errors will be discussed. In order to decrease the errors, Dynamic Relaxation method with modified time step (MFT) will be used. This procedure leads to an alternative algorithm which is very general and can be utilized with any implicit integration scheme. For numerical verification of the proposed technique, some single and multi degrees of freedom nonlinear dynamic systems will be analyzed. Moreover, results are compared with both exact and other available solutions. Suitable accuracy, high efficiency, simplicity, vector operations and automatic procedures are the main merits of the new algorithm in solving nonlinear dynamic problems.