• Structural Engineering and Mechanics
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• 제55권3호
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• pp.555-581
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• 2015

Triangular pyramid and Quadrangular pyramid elements for partial double-layer spherical reticulated shells of pyramidal system are investigated in the present study. Macro programs for six typical partial double-layer spherical reticulated shells of pyramidal system are compiled by using the ANSYS Parametric Design Language (APDL). Internal force analysis of six spherical reticulated shells is carried out. Distribution regularity of the stress and displacement are studied. A shape optimization program is proposed by adopting the sequence two-stage algorithm (RDQA) in FORTRAN environment based on the characteristics of partial double-layer spherical reticulated shells of pyramidal system and the ideas of discrete variable optimization design. Shape optimization is achieved by considering the objective function of the minimum total steel consumption, global and locality constraints. The shape optimization of six spherical reticulated shells is calculated with the span of 30m~120m and rise to span ratio of 1/7~1/3. The variations of the total steel consumption along with the span and rise to span ratio are discussed with contrast to the results of shape optimization. The optimal combination of main design parameters for six spherical reticulated shells is investigated, i.e., the number of the optimal grids. The results show that: (1) The Kiewitt and Geodesic partial double-layer spherical reticulated shells of triangular pyramidal system should be preferentially adopted in large and medium-span structures. The range of rise to span ratio is from 1/6 to 1/5. (2) The Ribbed and Schwedler partial double-layer spherical reticulated shells of quadrangular pyramidal system should be preferentially adopted in small-span structures. The rise to span ratio should be 1/4. (3) Grids of the six spherical reticulated shells can be optimized after shape optimization and the total steel consumption is optimized to be the least.

• 한국공간구조학회논문집
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• 제4권4호
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• pp.77-84
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• 2004

Researches on spherical shell which is most usually applied have been completed by many investigators already and generalized numerical formula was derived. But the existent researches are limited to those on spherical shell with isotropic or orthotropic roof stiffness, periodic distribution of roof stiffness that can be caused by spherical and latticed roof system is not considered. Therefore, the object of this study is to develop a structural analysis program to analyze spherical shells that have periodicity of roof stiffness distribution caused by latticed roof of large space structure, grasp buckling characteristics and behavior of structure.

• 한국공간구조학회논문집
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• 제2권4호
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• pp.45-52
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• 2002

Research about spherical shells been applying most usually is achieved by many investigators already and generalized equation has been derived. But, existent research is limited in case that spherical shell's roof rigidity is isotropy or orthotropy, and research that consider periodicity of rigidity-distribution that can happen by doing spherical shell's roof system by lattice system is not gone entirely. The purpose of this paper is applying Galerkin method to spherical shell that model periodicity of roof rigidity distribution that appear by roof lattice form of large space structure and develop structural analysis program that formularize. Rigidity-model of this research selects that of spherical shell which has 2-way grid. In this paper, buckling-strength and deformation distribution of isotopic spherical shell and 2-way grid spherical shell obtained by developed program could confirm the reliability by comparison with result of existent research.

• Structural Engineering and Mechanics
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• 제55권2호
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• pp.245-261
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• 2015

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies of eccentric hemi-spherical shells of revolution with variable thickness. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components $u_r$, $u_{\Theta}$, and $u_z$ in the radial, circumferential, and axial directions, respectively, are taken to be periodic in ${\theta}$ and in time, and algebraic polynomials in the r and z directions. Potential and kinetic energies of eccentric hemi-spherical shells with variable thickness are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to three or four-digit exactitude is demonstrated for the first five frequencies of the shells. Numerical results are presented for a variety of eccentric hemi-spherical shells with variable thickness.

• Advances in nano research
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• 제15권2호
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• pp.141-153
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• 2023

The main objective of this paper is to develop the finite element study on the nonlinear free vibration of functionally graded nanocomposite spherical shells reinforced with graphene platelets under the first-order shear deformation shell theory and von Kármán nonlinear kinematic relations. The governing equations are presented by introducing the full asymmetric nonlinear strain-displacement relations followed by the constitutive relations and energy functional. The extended Halpin-Tsai model is utilized to specify the overall Young's modulus of the nanocomposite. Then, the finite element formulation is derived and the quadrilateral 8-node shell element is implemented for finite element discretization. The nonlinear sets of dynamic equations are solved by the use of the harmonic balance technique and iterative method to find the nonlinear frequency response. Several numerical examples are represented to highlight the impact of involved factors on the large-amplitude vibration responses of nanocomposite spherical shells. One of the main findings is that for some geometrical and material parameters, the fundamental vibrational mode shape is asymmetric and the axisymmetric formulation cannot be appropriately employed to model the nonlinear dynamic behavior of nanocomposite spherical shells.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권5호
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• pp.473-483
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• 2017

Comprehensive consideration regarding influence mechanisms of initial imperfections on ultimate strength of spherical shells is taken to satisfy requirement of deep-sea structural design. The feasibility of innovative numerical procedure that combines welding simulation and non-linear buckling analysis is verified by a good agreement to experimental and theoretical results. Spherical shells with a series of wall thicknesses to radius ratios are studied. Residual stress and deformations from welding process are investigated separately. Variant influence mechanisms are discovered. Residual stress is demonstrated to be influential to stress field and buckling behavior but not to the ultimate strength. Deformations are proved to have a significant impact on ultimate strength. When central angles are less than critical value, concave magnitudes reduce ultimate strengths linearly. However, deformations with central angles above critical value are of much greater harm. Less imperfection susceptibility is found in spherical shells with larger wall thicknesses to radius ratios.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2004년도 춘계 학술발표회 논문집 제1권1호(통권1호)
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• pp.169-175
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• 2004

Researches on spherical shell which is most usually applied have been completed by many investigators already and generalized numerical formula was derived. But the existent researches are limited to those on spherical shell with isotropic or orthotropic roof stiffness, periodic distribution of roof stiffness that can be caused by spherical and latticed roof system is not considered. Therefore, this paper is to develop a structural analysis program to analyze spherical shells that have periodicity of roof stiffness distribution caused by latticed roof of large space structure, grasp buckling characteristics and behavior of structure.

• 한국공간구조학회논문집
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• 제2권3호
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• pp.115-122
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• 2002

It is often hard to obtain analytical solutions of boundary value problems of shells. Introducing some approximations into the governing equations may allow us to get analytical solutions of boundary value problems. Instead of an analytical procedure, we can apply a numerical method to the governing equations. Since the governing equations of shells of revolution under symmetric load are expressed by ordinary differential equations, a numerical solution of ordinary differential equations is applicable to solve the equations. In this paper, the governing equations of orthotropic spherical shells under symmetric load are derived from the classical theory based on differential geometry, and the analysis is numerically carried out by computer program of Runge-Kutta methods. The numerical results are compared to the solutions of a commercial analysis program, SAP2000, and show good agreement.

• Journal of electromagnetic engineering and science
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• 제1권1호
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• pp.11-17
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• 2001

In this paper, spherical Luneburg lens antennas have been systematically analyzed using the Eigenfunction Expansion Method (EEM), The developed technique has capability of performing a complete 3-D analysis to characterize the multi-layered dielectric spherical lens with arbitrary permittivity and permeability. This paper describes the analysis technique, and presents the results of the parametric study of Luneburg lens antennas by varying design parameters suoh as the diameter of the lens antenna (up to 80 wavelength), number of spherical shells (up to 30 shells), air-gaps between spherical shells, and dielectric loss of the material. Many representative engineering design curves including the far-field patterns, wide-angle sidelobe characterizations, antenna efficiency have been presented.

• Structural Engineering and Mechanics
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• 제56권5호
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• pp.813-833
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• 2015

Spherical reticulated shells are widely applied in structural engineering due to their good bearing capability and attractive appearance. Parametric modeling of spherical reticulated shells is the basis of internal analysis and optimization design. In the present study, generation methods of nodes and the corresponding connection methods of rod elements are proposed. Modeling programs are compiled by adopting the ANSYS Parametric Design Language (APDL). A shape optimization method based on the two-stage algorithm is presented, and the corresponding optimization program is compiled in FORTRAN environment. Shape optimization is carried out based on the objective function of the minimum total steel consumption and the restriction condition of strength, stiffness, slenderness ratio, stability. The shape optimization of four typical Schwedler spherical reticulated shells is calculated with the span of 30 m~80 m and rise to span ratio of 1/7~1/2. Compared with the shape optimization results, the variation rules of total steel consumption along with the span and rise to span ratio are discussed. The results show that: (1) The left and right rod-Schwedler spherical reticulated shell is the most optimized and should be preferentially adopted in structural engineering. (2) The left diagonal rod-Schwedler spherical reticulated shell is second only to left and right rod regarding the mechanical behavior and optimized results. It can be applied to medium and small-span structures. (3) Double slash rod-Schwedler spherical reticulated shell is advantageous in mechanical behavior but with the largest total weight. Thus, this type can be used in large-span structures as far as possible. (4) The mechanical performance of no latitudinal rod-Schwedler spherical reticulated shell is the worst and with the second largest weight. Thus, this spherical reticulated shell should not be adopted generally in engineering.