• Title/Summary/Keyword: Geometrically nonlinear finite element method

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Resisting Strength of Ring-Stiffened Cylindrical Steel Shell under Uniform External Pressure (균일외압을 받는 링보강 원형단면 강재 쉘의 강도특성)

  • Ahn, Joon Tae;Shin, Dong Ku
    • Journal of Korean Society of Steel Construction
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    • v.30 no.1
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    • pp.25-35
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    • 2018
  • Resisting strength of ring-stiffened cylindrical steel shell under uniform external pressure was evaluated by geometrically and materially nonlinear finite element method. The effects of shape and amplitude of geometric initial imperfection, radius to thickness ratio, and spacing of ring stiffeners on the resisting strength of ring-stiffened shell were analyzed. The resisting strength of ring-stiffened cylindrical shells made of SM490 obtained by FEA were compared with design strengths specified in Eurocode 3 and DNV-RP-C202. The shell buckling modes obtained from a linear elastic bifurcation FE analysis were introduced in the nonlinear FE analysis as initial geometric imperfections. The radius to thickness ratios of cylindrical shell in the range of 250 to 500 were considered.

On the Use of Modal Derivatives for Reduced Order Modeling of a Geometrically Nonlinear Beam (모드 미분을 이용한 기하비선형 보의 축소 모델)

  • Jeong, Yong-Min;Kim, Jun-Sik
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.4
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    • pp.329-334
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    • 2017
  • The structures, which are made up with the huge number of degrees-of-freedom and the assembly of substructures, have a great complexity. In order to increase the computational efficiency, the analysis models have to be simplified. Many substructuring techniques have been developed to simplify large-scale engineering problems. The techniques are very powerful for solving nonlinear problems which require many iterative calculations. In this paper, a modal derivatives-based model order reduction method, which is able to capture the stretching-bending coupling behavior in geometrically nonlinear systems, is adopted and investigated for its performance evaluation. The quadratic terms in nonlinear beam theory, such as Green-Lagrange strains, can be explained by the modal derivatives. They can be obtained by taking the modal directional derivatives of eigenmodes and form the second order terms of modal reduction basis. The method proposed is then applied to a co-rotational finite element formulation that is well-suited for geometrically nonlinear problems. Numerical results reveal that the end-shortening effect is very important, in which a conventional modal reduction method does not work unless the full model is used. It is demonstrated that the modal derivative approach yields the best compromised result and is very promising for substructuring large-scale geometrically nonlinear problems.

A Study on a Nonlinear Cable Finite Element (非線形 케이블 有限要素에 관한 硏究)

  • 장승필;박정일
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.1 no.1
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    • pp.93-101
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    • 1989
  • A geometrically nonlinear cable finite element is presented to use in the static or dynamic modeling of offshore and onshore structures such as guyed tower, tension leg platform or mooring buoy, submarine cable, cable-stayed bridge, suspension bridge, cable roof and so on. The cable finite element is derived directly from the compatibility equations and flexibility matrix of elastic catenary cable theory for the arbitary plane loading and geome try. A general and virsatile computer program has been developed to perform the analyses of cable member itself or cable guyed or suspened structures, in which Newmark-$\beta$ method is used to obtain a time domain solution and Newton-Raphson iteration method is used to solve the nonlinear system of compatibility equations of cable and algebraic static or dynamic equations at each time step. The results from the static and dynamic analysis of a cable member by the computer program are summarized and presented.

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Folding analysis of reversal arch by the tangent stiffness method

  • Iguchi, Shin-Ichi;Goto, Shigeo;Ijima, Katsushi;Obiya, Hiroyuki
    • Structural Engineering and Mechanics
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    • v.11 no.2
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    • pp.211-219
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    • 2001
  • This paper presents the tangent stiffness method for 3-D geometrically nonlinear folding analysis of a reversal arch. Experimental tests are conducted to verify the numerical analysis. The tangent stiffness method can accurately evaluate the geometrical nonlinearity due to the element translating as a rigid body, and the method can exactly handle the large rotation of the element in space. The arch in the experiment is made from a thin flat bar, and it is found that the folding process of the arch may be captured exactly by the numerical analysis with a model consisting of only 18 elements with the same properties.

Study of a Mixed Finite Element Model for the Analysis of a Geometrically Nonlinear Plate (기하학적 비선형 판재 해석을 위한 혼합형 FE Model 연구)

  • Kim, Woo-Ram;Choi, Youn-Dae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.10
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    • pp.1427-1435
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    • 2010
  • A mixed finite element model was developed using the classical plate theory to analyze the nonlinear bending of a plate. The appropriate weight functions for the constraints integrated over the domain were determined by the Lagrange multiplier method by using the principle of minimum virtual energy; which provides the constitutive relations between force-like variables and strains. All of detail terms of element wise coefficient matrices and associate tangent matrices to be used in the Newton iterative method are presented. Then, the linear solutions of the current model and those of the traditional displacement model under the SS (simple support) boundary conditions were compared with the existing analytical solution. The post-processed images of the nonlinear results of the force-like variables are presented to show the continuity of the solutions at the joint of the element boundaries. Finally, the converged nonlinear finite element solutions of the current model are compared with those of existing traditional displacement model.

Inelastic Nonlinear Analysis of Plane Truss Structures Using Arc-Length Method (호장법을 이용한 평면 트러스 구조의 비탄성 비선형 해석)

  • Kim, Kwang-Joong;Baek, Ki-Youl;Lee, Jae-Hong
    • Journal of Korean Association for Spatial Structures
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    • v.8 no.1
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    • pp.41-48
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    • 2008
  • Spatial structure is an appropriate shape that resists external force only with in-plane forte by reducing the influence of bending moment, and it maximizes the effectiveness of structure system. the spatial structure should be analyzed by nonlinear analysis regardless static and dynamic analysis because it accompanys large deflection for member. To analyze the spatial structure geometrical and material nonlinearity should be considered in the analysis. In this paper, a geometrically nonlinear finite element model for plane truss structures is developed, and material nonlinearity is also included in the analysis. Arc-length method is used to solve the nonlinear finite element model. It is found that the present analysis predicts accurate nonlinear behavior of plane truss.

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Nonlinear first ply failure analysis of composite skewed hypar shells using FEM

  • Ghosh, Arghya;Chakravorty, Dipankar
    • Structural Engineering and Mechanics
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    • v.68 no.1
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    • pp.81-94
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    • 2018
  • This paper uses the finite element method (FEM) considering geometrically nonlinear strains to study the first ply failure of laminated composite skewed hypar shell roofs through well-established failure criteria along with the serviceability criterion of deflection. Apart from validating the approach through solution of benchmark problems, skewed hypars with different practical parametric variations are studied for failure loads and tendencies. First ply failure zones are also identified to suggest design and non-destructive monitoring guidelines to the practising engineers. Recommendation tables regarding the design approaches to be adopted in specific cases and factor of safety values needed to be imposed on first ply failure load values for varying shell curvatures are also suggested in this paper. Providing practical inputs to design engineers is the main achievement of the present study.

A Nonlinear FEM Analysis of Connections Between Concrete Filled Steel Tube Columns and H-Beams (콘크리트충전(充塡) 각형강관(角形鋼管) 기둥과 H형강 보 접합부(接合部)의 비선형 유한요소해석)

  • Yun, Hyun-Do;Kim, Ok-Ryong;Kim, Ok-Ryong;Lee, Hun-Hee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.7 no.2
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    • pp.209-218
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    • 2003
  • The analytical studies included nonlinear finite element analysis of split-tee connection details subjected to axial load and lateral load. A three-dimensional model of the connections between CFT columns and H-beams has been developed. Both initial geometrical imperfections and residual stresses are taken into consideration. A geometrically nonlinear load-displacement analysis of the structure containing the imperfection is then performed, using the Riks method. Analytical results are compared with existing experimental results. Extensive parametric analyses are carried out to investigate the relation of the connections between CFT columns and H-beam to various parameters such as the axial load, column width-thickness ratio, and split-tee thickness.

Large deformation modeling of flexible manipulators to determine allowable load

  • Esfandiar, Habib;Korayem, Moharam H.;Haghpanahi, Mohammad
    • Structural Engineering and Mechanics
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    • v.62 no.5
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    • pp.619-629
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    • 2017
  • This paper focuses on the study of complete dynamic modeling and maximum dynamic load carrying capacity computation of N-flexible links and N-flexible joints mobile manipulator undergoing large deformation. Nonlinear dynamic analysis relies on the Timoshenko theory of beams. In order to model the system completely and precisely, structural and joint flexibility, nonlinear strain-displacement relationship, payload, and non-holonomic constraints will be considered to. A finite element solution method based on mixed method is applied to model the shear deformation. This procedure is considerably more involved than displacement based element and shear deformation can be readily included without inducing the shear locking in the element. Another goal of this paper is to present a computational procedure for determination of the maximum dynamic load of geometrically nonlinear manipulators with structural and joint flexibility. An effective measure named as Moment-Height Stability (MHS) measure is applied to consider the dynamic stability of a wheeled mobile manipulator. Simulations are performed for mobile base manipulator with two flexible links and joints. The results represent that dynamic stability constraint is sensitive when calculating the maximum carrying load. Furthermore, by changing the trajectory of end effector, allowable load also changes. The effect of torsional spring parameter on the joint deformation is investigated in a parametric sensitivity study. The findings show that, by the increase of torsional stiffness, the behavior of system approaches to a system with rigid joints and allowable load of robot is also enhanced. A comparison is also made between the results obtained from small and large deformation models. Fluctuation range in obtained figures for angular displacement of links and end effector path is bigger for large deformation model. Experimental results are also provided to validate the theoretical model and these have good agreement with the simulated results.

Wind loads and wind-resistant behaviour of large cylindrical tanks in square-arrangement group. Part 2: CFD simulation and finite element analysis

  • Liu, Qing;Zhao, Yang;Cai, Shuqi;Dong, Shilin
    • Wind and Structures
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    • v.31 no.6
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    • pp.495-508
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    • 2020
  • To investigate the structural behaviour of grouped tanks under wind loads, 2 problems need to be figured out, wind pressures on tank shells and critical loads of the shell under these pressure distribution patterns. Following the wind tunnel tests described in the companion paper, this paper firstly seeks to obtain wind loads on the external wall in a squarely-arranged cylindrical tank group by numerical simulation, considering various layouts. The outcomes demonstrate that the numerical method can provide similar results on wind pressures and better insights on grouping effects through extracted streamlines. Then, geometrically nonlinear analyses are performed using several selected potentially unfavourable wind pressure distributions. It is found that the critical load is controlled by limit point buckling when the tank is empty while excessive deformations when the tank is full. In particular, significant reductions of wind resistance are found on grouped full tanks compared to the isolated tank, considering both serviceability and ultimate limit state, which should receive special attention if the tank is expected to resist severe wind loads with the increase of liquid level.