Memorial University DAI: Structural integrity monitoring of a hydro-elastic model of a jacket platform

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Title	Structural integrity monitoring of a hydro-elastic model of a jacket platform
Author	Marshall, Mervin Allan
Description	Thesis (Ph.D.)--Memorial University of Newfoundland, 1991. Engineering and Applied Science
Date	1990
Pagination	xxxiii, 318 leaves : ill.
Subject	Offshore structures--Mathematical models; Offshore structures--Testing
Degree	Ph.D.
Degree Grantor	Memorial University of Newfoundland. Faculty of Engineering and Applied Science
Discipline	Engineering and Applied Science
Language	Eng
Notes	Bibliography: leaves 264-275.
Abstract	As a result of the increasing requirement for structural safety of offshore drilling platforms, the need for monitoring techniques capable of detecting damage of subsurface structural components increases. Since it is not possible, because of limited time constraints, to carry out tests on an actual operating platform in the ocean, an alternative solution is to experiment on a reduced model of an offshore structure. Very few experiments using a truly hydro-elastic model of a jacket platform have been published. -- This treatise deals with a detailed design and construction of a hydro-elastic model of a typical four-legged jacket offshore platform to carry out structural integrity monitoring. Both an indepth theoretical and experimental analysis were carried out. Experiments were conducted in a wave tank equipped with a pseudo random wave making facility. To obtain the necessary modal parameters (e.g., resonant frequencies, and damping ratios) from the ambient response data, the recently developed Marple algorithm was used with the very powerful Maximum Entropy Method (MEM). Regarding structural integrity monitoring, structural damage was simulated by saw cutting the member(s) under consideration. In the theoretical analyses, this was done by making the member(s) inactive in the analyses. The detection of damage was based on the changes in resonant frequencies compared with the intact structure. -- Resonant frequencies were determined for the intact and damaged structure and the results (i.e., experimental and theoretical) were compared to measure the influence of the damaged member(s) on the resonant frequencies of the structure. By cutting an inclined member in a k-braced panel to simulate damage of the member, a 39% decrease in the resonant frequency of the 2nd flexural mode was measured on the spectral density function of the wave induced vibration from the hydro-elastic model. The theoretical results showed a 29% decrease. (Theoretical results from the prototype structure showed similar trends.) -- Based on the reported results and evaluations, it was concluded that the resonant frequency changes clearly indicated the structure had been damaged. Besides, the theoretical analyses showed that the global modes most affected from the damage depended on the location of the damaged member(s).
Type	Text
Resource Type	Electronic thesis or dissertation
Format	Image/jpeg; Application/pdf
Source	Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries
Local Identifier	76083139
Rights	The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
Collection	Electronic Theses and Dissertations
Scanning Status	Completed
PDF File	(37.28 MB) -- http://collections.mun.ca/PDFs/theses/Marshall_MervinAllan2.pdf
CONTENTdm file name	270735.cpd