Reliability analysis of wake-induced collision of flexible risers

In the present paper, fatigue safety factors for flexible risers are assessed. A procedure for reliability analysis of wave-induced fatigue is first described. The procedure is based on performing a number of parametric studies with respect to variables that influence the fatigue lifetime. The results of these parametric studies are subsequently combined with models describing the statistical scatter of the same parameters. By application of this procedure, the safety factors which are required in order to reach specific target reliability levels can be computed. Such safety factors are computed for three specific flexible riser configurations. Different SN -curves which correspond to different corrosive environments are considered. The percentwise contribution from each parameter to the total statistical variation of the limit state function is also quantified.

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A Framework for Reliability-Based Fatigue Safety Factors for Flexible Risers

Volume 1: Offshore Technology; Special Symposium on Ocean Measurements and Their Influence on Design ◽

10.1115/omae2007-29487 ◽

2007 ◽

Author(s):

B. J. Leira ◽

K. A. Farnes ◽

R. T. Igland ◽

J. Martin ◽

D. Percy ◽

...

Keyword(s):

Reliability Analysis ◽

Safety Factors ◽

Fatigue Lifetime ◽

Specific Target ◽

Parametric Studies ◽

Flexible Risers ◽

Corrosive Environments ◽

Wave Induced

In the present paper, a procedure for reliability analysis of wave-induced fatigue in the tensile and pressure armours of flexible risers is described. The procedure is based on performing a number of parametric studies with respect to variables that influence the fatigue lifetime. The results of these parametric studies are subsequently combined with models describing the statistical scatter of the same parameters. By application of this procedure, the safety factors which are required in order to reach specific target reliability levels can be computed. Different SN-curves which correspond to different corrosive environments are considered.

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Safety Factors for Fatigue Analysis of Flexible Pipes Based on Structural Reliability

Volume 2: Structures, Safety and Reliability ◽

10.1115/omae2012-83586 ◽

2012 ◽

Author(s):

Fernando dos Santos Loureiro Filho ◽

Edison Castro Prates de Lima ◽

Luís Volnei Sudati Sagrilo ◽

Fernando Jorge Mendes de Sousa ◽

Carlos Alberto Duarte de Lemos

Keyword(s):

Reliability Analysis ◽

Structural Reliability ◽

Fatigue Analysis ◽

Design Criterion ◽

Flexible Riser ◽

Safety Factors ◽

Common Procedure ◽

Flexible Pipes ◽

Campos Basin ◽

Flexible Risers

Structural reliability–based methodology [1,2] has been proposed for fatigue analysis of flexible pipes tension armours. In this methodology a design criterion is verified using a standard reliability analysis approach and checking if the fatigue failure probability is equal to or less than a target value. The use of reliability analysis in the every day design practice is not yet a common procedure. Hence, in this paper we present the calibration of safety factors for Brazilian environmental conditions to be used in the standard fatigue analysis of flexible riser tension armours. The calibration is performed in order to guarantee the same target probability of failure. The safety factors are calibrated considering four flexible risers, two connected to FPSOs and the other two to semi-submersibles located in different water depths in Campos Basin offshore Brazil.

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