In lack of simultaneous data of metocean parameters such as wind, waves, and currents, Norwegian design regulations presently recommend a conservative combination of metocean parameters for estimation of characteristic metocean loads on offshore structures. A simplified parametric load model for a jacket, based on waves and currents, is assumed. Several approaches to load estimation are investigated and the following are considered: different averaging length of extreme currents, the effect of peak-over-threshold approach for estimation of extreme wave and currents compared to all-sea states approach and extreme load estimation directly from a load time series. When compared to the recommended approach, all other approaches yield a reduced estimated characteristic metocean load. The purpose of this study is to indicate the possible conservatism in the Norwegian design regulations for estimation of quasi-static loads on a jacket. The results are intended to be illustrative and not suitable for use in specific design calculations.

References

References
1.
NORSOK
,
2007
,
Norsok Standard N-003 Actions and Actions Effects
,
The Norwgian Oil Industry Association (OLF) and The Federation of Norwegian Industry
,
Lysaker, Norway
.
2.
Heideman
,
J. C.
,
1988
, “
Parametric Response Model for Wave/Current Joint Probability
,” American Petroleum Institute (API), Paper No. API-TAC 88-20
.
3.
Haver
,
S.
,
Eik
,
K. J.
, and
Nygaard
,
E.
,
2002
, “
Reliability Assessment of a Generic Jacket—Effects of Airgap Choices and Current Modelling
,”
ASME
Paper No. OMAE2002-28466.
4.
Reistad
,
M.
,
Breivik
,
Ø.
,
Haakenstad
,
H.
,
Aarnes
,
O. J.
,
Furevik
,
B. R.
, and
Bidlot
,
J. R.
,
2011
, “
A High-Resolution Hindcast of Wind and Waves for the North Sea, the Norwegian Sea, and the Barents Sea
,”
J. Geophys. Res.: Oceans
,
116
(
5
).
5.
Statoil
,
2010
,
Wam10 Wind Speed Adjustment—Validation
,
Statoil
,
Stavanger, Norway
.
6.
Statoil
,
2010
,
Wam10 Data Archive—Use of Wind and Wave Data Rev. 2
,
Statoil
,
Stavanger, Norway
.
7.
Statoil
,
2011
,
Nora10 Hindcast Wind Speed Versus Measurement
,
Statoil
,
Stavanger, Norway
.
8.
Francis
,
P. E.
,
1992
, “
Ness Summary Report
,” North European Storm Study (NESS) (1986–1991), Task Report No. 6010.
9.
Forristall
,
G. Z.
,
1978
, “
On the Statistical Distributions of Wave Heights in a Storm
,”
J. Geophys. Res.
,
83
(C
5
), pp.
2353
2358
.
10.
Faltinsen
,
O. M.
,
1990
,
Sea Loads on Ships and Offshore Structures
,
Cambridge University Press
,
Cambridge, UK
.
11.
Haver
,
S.
,
1985
, “
Wave Climate Off Northern Norway
,”
Appl. Ocean Res.
,
7
(
2
), pp.
85
92
.
12.
Tromans
,
P. S.
, and
Vanderschuren
,
L.
,
1995
, “
Response Based Design Conditions in the North Sea: Application of a New Method
,”
Offshore Technology Conference
, Paper No. OTC-7683.
13.
Næss
,
A.
, and
Moan
,
T.
,
2013
,
Stochastic Dynamics of Marine Structures
,
Cambridge University Press
,
Cambridge, UK
.
You do not currently have access to this content.