Título: | OPTIMIZATION OF SHELL STRUCTURES UNDER DYNAMIC LOADS | ||||||||||||||||
Autor: |
SUSANA ANGELICA FALCO MEIRA |
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Colaborador(es): |
LUIZ ELOY VAZ - Orientador SILVANA M B AFONSO DA SILVA - Coorientador |
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Catalogação: | 08/OUT/2001 | Língua(s): | PORTUGUESE - BRAZIL |
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Tipo: | TEXT | Subtipo: | THESIS | ||||||||||||||
Notas: |
[pt] Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio. [en] All data contained in the documents are the sole responsibility of the authors. The data used in the descriptions of the documents are in conformity with the systems of the administration of PUC-Rio. |
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Referência(s): |
[pt] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=2003&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=2003&idi=2 [es] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=2003&idi=4 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.2003 | ||||||||||||||||
Resumo: | |||||||||||||||||
The main goal of this work is to present a methodology and
a computer code which allow the designer, by means of
optimization techniques, to obtain efficient shapes of
plate and shell structures under linear-elastic behavior
and dynamic loads. With this objective, it is used the
optimization program SHELLD that includes the geometric
modeling, the mesh generation, the structural analysis by
the FEM, the sensitivity analysis and the structural
optimization algorithm. In this thesis, the geometry of the
free-form shell is represented by Coon surfaces, which are
formed by two series of cubic splines intercepting the key
points, which lay on the midsurface.Once the shell surface
is discretized in finite elements, the structural analysis
starts. The structural response analysis is performed by
means of the Newmark direct integration method.
The finite element used is the 9 nodes Huang-Hinton
element, which belongs to the family of elements
degenerated from 3D elements.The aim of the sensitivity
analysis is to determine gradients of the objective
functions and constraints of the design optimization
problem with respect to the design variables. The method
used in this work for performing the sensitivity analysis
is based on the total differentiation of the discrete
dynamic equilibrium equations and derivatives of stiffness,
mass and damping matrices are performed by means of the
finite difference method. This methodology is known in
the literature as the Semi-analytical Method for
sensitivity analysis. The sizing and shape variables are
the thickness and the lengths of the radii in the key
points respectively, which implies in a decrease of the
number of variables in the project. The design of shell
structures under dynamic loads is a common problem in
engineering practice. In order to obtain an optimal design
of these structures one generally tries to keep as
low as possible their weight or volume, in one word their
cost, while constraining their structural response in terms
of displacements, accelerations, frequencies or stress
resultants. Alternatively one can minimize the displacement
or acceleration at some point of the structure or its global
displacement while keeping its volume constant. In the case
of free vibration the objective is to maximize the
frequency, corresponding to the vibration mode one wants to
stiffen, keeping the shell volume constant. In special
cases of shells with multiple eigenvalues, try to keep as
low as possible their volume considering frequency
constrains to avoid clusters.To solve the nonlinear
constrained optimization problem at hand the Sequential
Quadratic Programming algorithm (SQP) from NAG library of
FORTRAN is used. In this thesis, we have placed more
emphasis on how to formulate optimization problems
appropriately rather than on the theory underlying
-mathematical programming- optimization algorithms, i.e. we
use the SQP algorithm essentially as -black box-.
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