• Structural Engineering and Mechanics
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• v.20 no.4
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• pp.405-420
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• 2005

In this paper, a hybrid/mixed nonlinear shell element is developed in polar coordinate system based on Hellinger/Reissner variational principle and the large-deflection theory of plate. A numerical solution scheme is formulated using the hybrid/mixed finite element method (HMFEM), in which the nodal values of bending moments and the deflection are the unknown discrete parameters. Stability of the present element is studied. The large-deflection analyses are performed for simple supported and clamped circular plates under uniformly distributed and concentrated loads using HMFEM and the traditional displacement finite element method. A parametric study is also conducted in the research. The accuracy of the shell element is investigated using numerical computations. Comparisons of numerical solutions are made with theoretical results, finite element analysis and the available numerical results. Excellent agreements are shown.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.228-234
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• 2013

This study focuses on development of a finite element model for analysis of thermal characteristics of a direct-connection spindle of a machining center by joint simulation of heat transfer and thermal deformation. Two finite element analyses were carried out procedurally for heat transfer, first, to identify temperature distribution of components of the spindle and then for thermal deformation to identify their structural behavior based on the temperature distribution. It was assumed that the heat transfer between a component revolving and the surrounding air is identical to that between a flat plate and the running air on it and the heat transfer is based on a uniform surface heat flux for turbulent flow. The results from the analyses were compared with those from experiments to validate the finite element model.

• Structural Engineering and Mechanics
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• v.6 no.6
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• pp.693-710
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• 1998

This paper concerns studies on the shape formation of post-tensioned and shaped steel domes. The post-tensioned and shaped steel domes, assembled initially at ground level in an essentially flat condition, are shaped to a curved space form and erected into the final position by means of a post-tensioning technique. Based on previous studies on this shape formation principle, three post-tensioned and shaped steel domes have been constructed. The results of the shape formation tests and finite element analyses are reported in this paper. It is found that the first two test domes did not furnish a part-spherical shape as predicted by finite element analyses, because the movements of some mechanisms were not controlled sufficiently. With a revised post-tensioning method, the third dome obtained the theoretical prediction. The test results of the three post-tensioned and shaped domes have shown that a necessary condition to form a desired space shape from a planar layout with low joint stiffnesses is that the movements of all the existing mechanisms must be effectively controlled as indicated by the finite element analysis. The extent of the maximum elastic deformation of a post-tensioned and shaped steel structure is determined by the strength of the top chords and their joints. However, due to the semi-rigid characteristic of the top chord joints, the finite element analyses cannot give a close prediction for the maximum elastic deformations of the post-tensioned and shaped steel domes. The results of the current studies can be helpful for the design and construction of this type of structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.373-380
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• 1998

3D finite element analyses of movable bearing shoe and hinged bearing shoe are performed. The finite element models are built using MSC/PATRAN and analyses are carried out using MSC/NASTRAN. Results are again completely processed using MSC/PATRAN. From the results of the analyses, trends of deformation and stress distribution are reviewed and important factors to consider in the design of bearing shoes are discussed. Furthermore optimum crowning amount for the roller of movable bearing shoe was determined according to the results of the analyses.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1518-1525
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• 2006

Finite element analyses of structures made of the fiber reinforced composites require an adequate method to characterize the high anisotropic behavior induced by one or several layers of fiber cords with different spatial orientation embedded in a rubber matrix. This paper newly proposes a continuum based rebar element considering change of the orientation of the fiber during deformation of the composite. The mechanical behavior of the embedded fiber is modeled using two-node bar elements in order to consider the relative deformation and spatial orientation of the embedded fiber. For improvement of the analysis accuracy, the load-displacement curve of fiber is applied to the stiffness matrix of fiber. A finite element program is constructed based on the total Lagrangian formulation considering both geometric and material nonlinearity. Finite element analyses of the tensile test are carried out in order to evaluate the validity of the proposed method. Analysis results obtained with the proposed method provides realistic representation of the fiber reinforced rubber composite compared to results of other two models by the Halpin-Tsai equation and a rebar element in ABAQUS/Standard.

• Structural Engineering and Mechanics
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• v.9 no.1
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• pp.89-97
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• 2000

A modified constitutive model has been developed for nonlinear finite element analysis of axisymmetric reinforced concrete structures, and then implemented into an existing finite element program. By comparing with the experimental results available, the present model has been validated.

• Computers and Concrete
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• v.15 no.2
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• pp.259-277
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• 2015

The lack of experimental studies on the mechanical behavior of reinforced concrete (RC) haunched beams leads to difficulties in statistical and reliability analyses. This study performs stochastic and reliability analyses of the ultimate shear capacity of RC haunched beams based on nonlinear finite element analysis. The main aim of this study is to investigate the influence of uncertainty in material properties and geometry parameters on the mechanical performance and shear capacity of RC haunched beams. Firstly, 65 experimentally tested RC haunched beams and prismatic beams are analyzed via deterministic nonlinear finite element method by a special program (ATENA) to verify the efficiency of utilized numerical models, the shear capacity and the crack pattern. The accuracy of nonlinear finite element analyses is verified by comparing the results of nonlinear finite element and experiments and both results are found to be in a good agreement. Afterwards, stochastic analyses are performed for each beam where the RC material properties and geometry parameters are assigned to take probabilistic values using an advanced simulating procedure. As a result of stochastic analysis, statistical parameters are determined. The statistical parameters are obtained for resistance bias factor and the coefficient of variation which were found to be equal to 1.053 and 0.137 respectively. Finally, reliability analyses are accomplished using the limit state functions of ACI-318 and ASCE-7 depending on the calculated statistical parameters. The results show that the RC haunched beams have higher sensitivity and riskiness than the RC prismatic beams.

• Steel and Composite Structures
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• v.28 no.4
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• pp.415-426
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• 2018

This paper presents a multi-layer finite element for buckling and free vibration analyses of laminated beams based on a higher-order layer-wise theory. An N-layer beam element with (9N + 7) degrees-of-freedom is proposed for analyses. Delamination and slip between the layers are not allowed. Element matrices for the single- and multi-layer beam elements are derived by Lagrange's equations. Buckling loads and natural frequencies are calculated for different end conditions and lamina stacking. Comparisons are made to show the accuracy of proposed element.

• Computational Structural Engineering
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• v.10 no.2
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• pp.139-148
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• 1997

A finite element method is programmed to analyse the nonlinear behavior of axisymmetric structures. The lst order Mindlin shell theory which takes into account the transversal shear deformation is used to formulate a conical two node element with six degrees of freedom. To evade the shear locking phenomenon which arises in Mindlin type element when the effect of shear deformation tends to zero, the reduced integration of one point Gauss Quadrature at the center of element is employed. This method is the Updated Lagrangian formulation which refers the variables to the state of the most recent iteration. The solution is searched by Newton-Raphson iteration method. The tangent matrix of this method is obtained by a finite difference method by perturbating the degrees of freedom with small values. For the moment this program is limited to the analyses of non-linear elastic problems. For structures which could have elastic stability problem, the calculation is controled by displacement.

• Transactions of Materials Processing
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• v.4 no.1
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• pp.92-104
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• 1995

It often happens some elements are so largely distorted during a large-deformation finite element analysis that further calculation becomes impossible or the approximation error increases rapidly. This problem can be overcomed only by remeshing at several suitable stages. The present study aimed to establish the criterion based on the error estimators, and examined in the simulation and posterior error analysis of ring compression test to demonstrate the usefulness of them. The distribution of each error estimator and its variation during deformation were investigated. All the error estimators were increased monotonously with deformation and decreased rapidly at remeshing stage. It was shown that the error estimators suggested in this study are good measures as remeshing criterion for large deformation finite element analyses.