Título: | APPLICATION OF NONLINEAR VIBRATION MODES TO CONCEPTUAL MODELS OF OFFSHORE STRUCTURES | |||||||
Autor: |
ELVIDIO GAVASSONI NETO |
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Colaborador(es): |
PAULO BATISTA GONCALVES - Orientador DEANE DE MESQUITA ROEHL - Coorientador |
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Catalogação: | 08/MAR/2013 | 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=21272&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=21272&idi=2 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.21272 | |||||||
Resumo: | ||||||||
The increasing water depth and the ocean adverse environment demand
more accurate vibration analysis of offshore structures. Due to large amplitude
oscillations, a nonlinear vibration analysis becomes necessary. Numerical
methods such as finite element constitute a computationally expensive task when
applied to these problems, since the occurrence of modal coupling demands a high
number of degrees-of-freedom. A feasible possibility to overcome these
difficulties is the use of low order models. The nonlinear normal modes have been
shown to be an effective tool in the derivation of reduced order models in
nonlinear dynamics. In the use of nonlinear modal analysis fewer modes are
required to achieve a given level of accuracy in comparison to the use of linear
modes. This work uses the nonlinear normal modes to derive low dimensional
models to study the vibration of simplified models of offshore structures. Three
examples are considered: an inverted pendulum, an articulated tower and a spar
platform. Both free and forced vibrations are studied. The asymptotic and
Galerkin-based methods are used to derive the normal modes. In addition, an
alternative numerical procedure to construct such modes is proposed, which can
be used to derive coupled modes. The solution stability is determined by the use
of the Floquet theory, bifurcation and Mathieu diagrams, and Poincaré sections.
The Poincaré sections are also used to investigate the multiplicity of modes and
multimodes. The results obtained from the numerical integration of the original
system are favourably compared with those of the reduced order models, showing
the accuracy of the reduced models.
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