Quantitative reliability and integrity analysis of steel catenary risers (SCRs) can provide important information about their safety and toward their cost-effective and optimal design. SCRs are one of the commonly used riser systems in offshore production stations. The consequence of an SCR failure is significant; however, the overall safety of the riser is typically not quantified. Especially, because of the uncertainties associated with environmental conditions and structural capacities, quantitative reliability methods can take advantage of available data and developments in computing technology to provide a strong basis for their reliable engineering decision making. This paper presents a simplified approach for assessing the strength and fatigue reliability of SCRs, accounting for the uncertainties with their yield strength and fatigue capacities as well as the environmental conditions. Moreover, the integrity-based optimal design of riser strength limit state for a target annual probability of failure is discussed. The fatigue reliability of the SCR system is also assessed in component and system levels. The proposed method is then applied to a typical SCR attached to a semisubmersible vessel under Gulf of Mexico (GOM) conditions. Results of dynamic (time-domain) analyses under various environmental conditions are used to quantify the SCR safety and integrity and to optimize its design for a target annual probability of strength failure. By estimating the riser system probability of strength and fatigue failure in its lifetime, the strength and fatigue integrity indices, and the optimality factors of the riser sections for the strength limit state, suggestions are provided to improve the riser design. For example, it was found that considering the two main limit states of strength and fatigue failure of the SCR system, a strength failure at the taper stress joint (TSJ) is the likely mode of failure in this riser system, which has a probability of 0.0035 in its 25 year lifetime.

References

References
1.
Mousavi
,
M.
, and
Gardoni
,
P.
,
2013
, “
Integrity Index and Integrity-Based Optimal Design of Structural Systems
,”
J. Eng. Struct.
,
60
, pp.
206
213
.
2.
Li
,
F. Z.
, and
Low
,
Y. M.
,
2012
, “
Fatigue Reliability Analysis of a Steel Catenary Riser at the Touchdown Point Incorporating Soil Model Uncertainties
,”
J. Appl. Ocean Res.
,
38
, pp.
100
110
.
3.
Khan
,
R. A.
, and
Ahmad
,
S.
,
2007
, “
Safety of a Deep Water Marine Riser Under Random Loads
,”
Proc. Inst. Civ. Eng.: Maritime Eng.
,
160
(
4
), pp.
175
183
.
4.
Nazir
,
M.
,
Khan
,
F.
, and
Amyotte
,
P.
,
2008
, “
Fatigue Reliability Analysis of Deep Water Rigid Marine Risers Associated With Morison-Type Wave Loading
,”
J. Stochastic Environ. Res. Risk Assess.
,
22
(
3
), pp.
379
390
.
5.
He
,
J.
, and
Low
,
Y.
,
2012
, “
An Approach for Estimating the Probability of Collision Between Marine Risers
,”
J. Appl. Ocean Res.
,
35
, pp.
68
76
.
6.
Mousavi
,
M.
,
Upadhye
,
S.
, and
Haverty
,
K.
,
2014
, “
Simplified Strength Reliability and Integrity Analysis of TTRs
,”
ASME
Paper No. OMAE2014-24289.
7.
Mousavi
,
M.
,
Upadhye
,
S.
,
Vijayaraghavan
,
V.
, and
Haverty
,
K.
,
2014
, “
A Probabilistic Approach to Fatigue Safety and Integrity Analysis of TTRs
,”
ASME
Paper No. OMAE2014-24294.
8.
Mousavi
,
M.
, and
Gardoni
,
P.
,
2014
, “
A Simplified Method for Reliability- and Integrity-Based Design of Engineering Systems and Its Application to Offshore Mooring Systems
,”
J. Mar. Struct.
,
36
, pp.
88
104
.
9.
Ang
,
A.
, and
Tang
,
W.
,
2007
,
Probability Concepts in Engineering: Emphasis on Applications in Civil and Environmental Engineering
,
Wiley
,
Hoboken, NJ
, p.
57
.
10.
Gardoni
,
P.
,
Der Kiureghian
,
A.
, and
Mosalam
,
K.
,
2002
, “
Probabilistic Capacity Models and Fragility Estimates for Reinforced Concrete Columns Based on Experimental Observations
,”
J. Eng. Mech.
,
128
(
10
), pp.
1024
1038
.
11.
API
,
2013
,
Dynamic Risers for Floating Production Systems
,
2nd ed.
,
American Petroleum Institute, Standard 2RD
,
Washington, DC
, p.
71
.
12.
Ang
,
A.
, and
Tang
,
W.
,
2007
,
Probability Concepts in Engineering: Emphasis on Applications in Civil and Environmental Engineering
,
Wiley
,
Danvers, MA
.
13.
Box
,
G.
, and
Tiao
,
G.
,
1992
,
Bayesian Inference in Statistical Analysis
,
Wiley-Interscience
,
Toronto, Canada
, p.
113
.
14.
BS
,
1993
,
Code of Practice for Fatigue Design and Assessment of Steel Structures
,
British Standards Institution, BS 7608
,
London, UK
, p.
31
.
15.
DNV
,
2010
,
Dynamic Risers
,
Det Norske Veritas
, Offshore Standard OS-F201, pp.
17
, 68.
16.
DNV
,
1995
, “
Guideline for Structural Reliability Analysis General
,” Det Norske Veritas, Report No. 95-2018, pp.
293
294
.
17.
30 CFR 250.1002
,
2005
, “
Oil and Gas and Sulphur Operations in the Outer Continental Shelf (OCS)-Fixed and Floating Platforms and Structures and Documents Incorporated by Reference
,” Code of Federal Regulations.
18.
49 CFR
,
2009
, “
Subpart C&D: Transportation-Document for Codification of Documents of General Applicability and Future Effect
,” Code of Federal Regulations.
19.
Wood Group Kenny
,
2009
,
Flexcom 7.9.7–MCS Software Reference Manual
,
Dublin 2
,
Ireland
.
20.
API
,
2012
,
Specification for Line Pipe
,
45th ed.
,
American Petroleum Institute, Specification 5L
,
Washington, DC
.
21.
API
,
2007
,
Interim Guidance on Hurricane Conditions in the Gulf of Mexico
,
1st ed.
,
American Petroleum Institute
, Report 2MET,
Washington, DC
.
22.
Jonathan
,
P.
, and
Ewans
,
K.
,
2007
, “
The Effect of Directionality on Extreme Wave Design Criteria
,”
J. Ocean Eng.
,
34
(
14
), pp.
1977
1994
.
23.
Baxter
,
C.
,
Schutz
,
R.
, and
Caldwell
,
C.
,
2007
, “
Experience and Guidance in the Use of Titanium Components in Steel Catenary Riser Systems
,”
Offshore Technology Conference
,
Houston, TX
, Apr. 30–May3, Paper No. OTC-18624-MS.
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