文档介绍：Assessment of existing offshore structures
for life extension
Doctorial Thesis by
Gerhard Ersdal
Thesis submitted as partial fulfilment of
the requirements for the degree of Doktor Ingeniør
Faculty of Science and Technology
Department of Mechanical and Structural Engineering and Material Science
October 2005
University of Stavanger
N-4036 Stavanger
NORWAY
©2005 Gerhard Ersdal
ISBN 82-7644-273-0
ISSN 0809-6775
ii
Abstract
The subject of this thesis is evaluation of possible life extension of existing offshore jacket
structures. This thesis is a contribution to the further development of the theoretical
background for the procedures and standards in life extension of offshore installations. The
relevant standards for life extension of existing offshore jacket structures are reviewed, with
focus on ultimate limit state analysis and fatigue analysis. In general, it can be said that the
existing standards and procedures mend assessment of existing structures for life
extension based on: 1) Linear analysis ponent checks, 2) Non-linear system strength
analysis ponent checks, and 3) Structural reliability analysis for the ultimate limit
state check and: 1) SN fatigue analysis, 2) Fracture mechanics crack growth analysis, and 3)
Structural reliability analysis for the fatigue limit state.
This thesis proposes that a risk evaluation of an ageing structure is needed as a part of the
assessment. Such a risk evaluation should include identification of hazards and failure
modes, and possibly include an identification of the preventive measures (barriers) for
reducing the likelihood of these hazards and failure modes. A review of hazards and failure
modes for an ageing offshore jacket structure are presented, and preventive actions to limit
the hazards have been investigated using a barrier analysis approach. It is concluded that a