The loading and reliability of fixed steel structures in extreme seas: recent advances and required improvements
Author(s)
Swan, Chris
Latheef, Mohamed
Ma, Li
Ma, Li
Type
Conference Paper
Abstract
is paper concerns the calculation of the fluid loads acting on a steel jacket structure, as required for a structural reliability assessment. It addresses both the sub-structure loads and the wave-in-deck loads, highlighting the practical implications of recent advances in the description of extreme ocean waves. These advances include the nonlinear amplification
of crest elevations beyond second-order, the occurrence of wave breaking (both spilling and over-turning), the role of directionality (particularly in relation to the highest and steepest individual waves), the local and rapid spatial evolution, and the description of the water particle kinematics high in the wave crest. Taken together, these changes ensure that the load statistics
will be very different to those based on linear or second-order theory. Moreover, the maximum loads relating to small exceedence probabilities will differ from deterministic calculations based on un-physical regular wave theories; the fifth-order Stokes solution being commonly adopted in present practice. Calculations undertaken to date suggest that present practice is likely to be conservative in respect of sub-structure loads, but non-conservative in terms of wave-in-deck loads; the latter potentially becoming very significant when large levels of wave inundation are concerned. In addressing these issues, recommendations are made concerning the implementation of improved modelling approaches; the ultimate goal being to achieve a physically realistic solution (including the effects of wave breaking) without the need for excessive laboratory or numerical calculations.
of crest elevations beyond second-order, the occurrence of wave breaking (both spilling and over-turning), the role of directionality (particularly in relation to the highest and steepest individual waves), the local and rapid spatial evolution, and the description of the water particle kinematics high in the wave crest. Taken together, these changes ensure that the load statistics
will be very different to those based on linear or second-order theory. Moreover, the maximum loads relating to small exceedence probabilities will differ from deterministic calculations based on un-physical regular wave theories; the fifth-order Stokes solution being commonly adopted in present practice. Calculations undertaken to date suggest that present practice is likely to be conservative in respect of sub-structure loads, but non-conservative in terms of wave-in-deck loads; the latter potentially becoming very significant when large levels of wave inundation are concerned. In addressing these issues, recommendations are made concerning the implementation of improved modelling approaches; the ultimate goal being to achieve a physically realistic solution (including the effects of wave breaking) without the need for excessive laboratory or numerical calculations.
Editor(s)
Ma, Li
Date Issued
2016-09-14
Date Acceptance
2016-05-14
Citation
The third Offshore Structure Reliability Conference, OSRC, 2016
Journal / Book Title
The third Offshore Structure Reliability Conference, OSRC
Copyright Statement
© 2016 The Author(s).
Source
The Third Offshore Structure Reliability Conference, OSRC
Publication Status
Published
Start Date
2016-09-14
Finish Date
2016-09-16
Coverage Spatial
Stavanger, Norway