• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.399-407
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• 2002

A three-dimensional method of analysis is presented for determining the free vibration frequencies and mode shapes of hollow bodies of revolution (i.e., thick shells), not limited to straight line generators or constant thickness. The middle surface of the shell may have arbitrary curvatures, and the wall thickness may vary arbitrarily. Displacement components$U_\Phi, U_z, U_\theta$ in the meridional, normal and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in$\theta$, and algebraic polynomials in the$\Phi$and z directions. Potential(strain) and kinetic energies of the entire body are formulated, and upper bound values of the frequencies are obtained by minimizing the frequencies. As the degrees of the polynomials are increased, frequencies converge to the exact values. Novel numerical results are presented for two types of thick conical shells and thick spherical shell segments having linear thickness variations. Convergence to four digit exactitude is demonstrated for the first five frequencies of both types of shells. The method is applicable to thin shells, as well as thick and very thick ones.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.481-494
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• 2001

An enhanced degenerated shell finite element (FE), which has been developed for inelastic analysis of reinforced concrete structures is described in this paper. Generally, Reissner-Mindlin (RM) assumptions are adopted to develop the degenerated shell FE so that transverse shear deformation effects is considered. However, it is found that there are serious defects such as locking phenomena in RM degenerated shell FE since the stiffness matrix has been overestimated in some situations. As remedies of locking phenomena, reduced integration, incompatible mode and assumed strain method have been used. Especially, the assumed strain method has been successfully used in many FEs. But contrarily, there is a few investigation on the performance of the assumed strains in the inelastic analysis of concrete structures. Therefore, shell formulation is provided in this paper with emphasis on the terms related to the stiffness matrix based on assumed strain method and microscopic concrete material model. Finally, the performance of the present shell element is tested and demonstrated with several numerical examples. From the numerical tests, the present result shows a good agreement with experimental data or other numerical results.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.373-384
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• 1999

The shell structures with composite materials have the advantages in strength, corrosion resistance, and weight reduction. The objective of this study is to analyze anisotropic composite circular cylindrical shells with shear deformation theory. In applying numerical methods to solve differential equations of anisotropic shells, this paper use finite difference method. The accuracy of the numerical method can be improved by taking higher order of interval ${\Delta}$ to reduce error. This study compares the results of finite difference method with the results of ANSYS based on finite element method. Several numerical examples show the advantages of the stiffness increasement when the composite materials aroused. Therefore, it is expected that results of this study give various guides for change of the subtended angles, load cases, boundary conditions, and side-to-thickness ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.409-415
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• 2011

Optimization Analysis of angle-ply laminated shells, having one pair of opposite edges supported, are investigated on the basis of the first-order shear deformation theory. The equations of motion of the shell are solved by the use of ritz method. A range of results are presented for composite shells to show the effects of lamination angle and number of layers on natural frequency. In addition, an analysis of the strain energy distributions is used as an aid for the better understanding of the vibration characteristics of the shells.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.197-208
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• 2000

Choi et al./sup 1)/ presented the total Lagrangian formulation based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors and taking into account the second order rotation terms in the incremental displacement field. Assumed strain concept is adopted in order to overcome the shear locking phenomena and to eliminate the spurious zero energy mode. In this paper, for the ultimate strength analysis of stiffened shell structures considering effects of residual stresses, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to anisotropic shell structures. In addition, the load/displacement incremental scheme is adopted for non-linear F.E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with the results in literatures.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.639-648
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• 2000

A model analysis is used to predict the impact response of a simply supported elastic circular cylindrical shell composed of two bonded isotropic layers. The governing equations for a two-layered cylindrical shell are derived on the basis of an improved theory for the single-layer shell which includes the effects of transverse shear deformation and rotary inertia. Calculations are made for the specific case of the steel-concrete cylindrical shell subjected to a suddenly applied load. The solutions show that the method yields very good results. Therefore the proposed method is useful not only for a better investigating of the response characteristics of the shell but also available for a check on other numerical methods such a FEM.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.46-53
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• 2005

Compare to the large number of curved quadrilateral degenerated-shell elements, there are only a very few curved triangular degenerated-shell elements. Based on the assumed natural strain sampling scheme previously developed for a quadratic degenerated-shell element for linear analysis, this paper devises geometric non-linear six-node degenerated-shell element. The element can be curved and is only equipped with the standard nodal d.o.f.'s. Careful consideration has been exercised to circumvent various locking phenomena that plague degenerated-shell element. Numerical examples are presented to illustrate efficiency.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.87-98
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• 2012

In this study, mechanical role of edge beams in the gabled hyperbolic paraboloid shells was investigated through the comparisons of Finite element(FE) analysis results between the shells structures with and without edge beams. In addition, the effects of roof slope was studied. FE analysis showed that roof loads was directly transferred to the supports at corners by the arch action in the diagonal direction of the shells, thus, less member forces in the edge and ridge beams but higher stresses near supports were estimated than those from the membrane theory. When the edge beams were removed, stress concentration in the shells near the supports and the deflections along the shell edge were increased. Such phenomenon were intensified as the roof slope decrease. Thus, in gable hyperbolic paraboloid shell, the thickness of the shell near supports needs to be increased and careful investigation should be made in the cases when the roof height is low and/or the edge beams are removed.

• Composites Research
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• v.12 no.5
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• pp.65-79
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• 1999

This paper descrives the method to analyzed the free vibratioin of supported composite cylindrical shells with a longitudinal, interior rectangular plate. To obtain the free vibration characteristics before the combination of two structures, the energy principle based on the classical plate theory and Love's thin shell theory is adopted. The frequency equation of the combined system is formulated using the receptance method. When the line load and moment applied along the joint are assumed as the the Dirac delta and sinusolidal function, the continuity conditions at the joint of the plate and shell are proven to be satisfied. The effects on the combined shell frequencies of the length-no-radius ratios and radius-to-thickness ratios of the shell, fiber orientation angles and orthotropic modulus ratios of the composite are also examined.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.11-21
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• 2008

A linear and non-linear analysis for plates and shells with arbitrary edge supports subjected to various loading was presented. The 9-node ANS(Assumed Natural Strain) hell element was employed and the spring element, which could express an arbitrary edge support using the six degrees of freedom, was introduced. For the application of his analysis, the plates and shells with various edge supports were analyzed, and the ending behavior with these edge supports were obtained accurately. For these edge supports, particularly elastic edge support was simulated by six springs and reasonable results were obtained. The results show that the present method can be widely used to analyze the bending behavior of plates and shells with arbitrary edge conditions.