Chaotic response and stability of offshore equipment Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/nz806332b

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • This investigation deals with the chaotic rocking response and overturning stability of offshore equipment subjected to base excitations due to wave-induced motions of the supporting compliant offshore structural system. The equipment compliant structural system is modelled as a free-standing rigid object subjected to horizontal and vertical base accelerations. Three of the major goals of this study are: (1) to identify the major sources of nonlinearity and sensitivity which make the response of the objects difficult to predict and experiments with identical set up and excitations unrepeatable; (2) to develop analytical and quantitative measures to characterize the sensitivity of the response using modern geometric methods; and (3) to determine the relative influence of the various nonlinearities and system parameters on the rocking behavior and overturning stability. Four major sources of nonlinearity are examined in detail. The first source is due to the transition of governing equations after impact when the center of rotation changes from one edge to the other. The second is due to the abrupt change in angular velocity at impact and the associated energy dissipation. The third is due to the geometric effect of the finite slenderness ratio of the object. The fourth is due to the coupling of the vertical (parametric) excitation with the rocking response. To isolate the influence of each source of nonlinearity on the chaotic response and overturning stability, several realistic approximate models containing different combinations of the nonlinearities are examined. Analytical and numerical procedures are developed to determine the motion of rigid objects. It is demonstrated that the nonlinearity associated with the transition of governing equations after impact produces responses that cannot be predicted by classical nonlinear stability analysis. Modern geometric methods are needed to delineate these unanticipated responses. Two new types of stable responses are discovered. In addition to the periodic and overturning responses predicted by classical stability analysis, the Melnikov method and numerical results show the existence of quasi-periodic, and chaotic responses. The stability region of each of the four types of responses --periodic, quasi-periodic, chaotic, and overturning -- are found to be sensitively dependent on the damping, geometry, and the parametric excitation nonlinearities as well as initial conditions and excitation amplitude and frequency parameters. It is found that although the individual responses are very sensitive to small changes in the system and excitation parameters, the following general trends are observed: (1) increasing damping decreases the stability region of the chaotic responses; (2) increasing slenderness ratio increases the stability region of the chaotic responses; and (3) increasing relative magnitude of parametric excitation increases the stability region of the chaotic responses.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome) using Capture Perfect 3.0.82 on a Canon DR-9080C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Deborah Campbell(deborah.campbell@oregonstate.edu) on 2013-06-18T15:13:32Z (GMT) No. of bitstreams: 1 LinHuan1990.pdf: 736362 bytes, checksum: ee22af2222d584987691277a462360e9 (MD5)
  • description.provenance : Submitted by Kim Stowell (ksscannerosu@gmail.com) on 2013-05-07T23:53:17Z No. of bitstreams: 1 LinHuan1990.pdf: 736362 bytes, checksum: ee22af2222d584987691277a462360e9 (MD5)
  • description.provenance : Made available in DSpace on 2013-06-18T15:13:32Z (GMT). No. of bitstreams: 1 LinHuan1990.pdf: 736362 bytes, checksum: ee22af2222d584987691277a462360e9 (MD5) Previous issue date: 1990-04-27
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-05-08T16:05:55Z (GMT) No. of bitstreams: 1 LinHuan1990.pdf: 736362 bytes, checksum: ee22af2222d584987691277a462360e9 (MD5)

Relationships

Parents:

This work has no parents.

Last modified

Downloadable Content

Download PDF

Items