Assessment of a probabilistic approach for design of dynamic flexible risers

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:398027

Hanson, T D; Nilsen, A U

In this work a reliability based method for design of flexible risers is investigated. Two different riser configurations are addressed, one a 6 inch dynamic mud jumper suspended between a semisubmersible support vessel and a jacket. The other is a 15 inch lazy-S gas export riser attached to a floating production unit at approximately 300 meters water depth. ULS failure modes are considered in this study. A finite element analysis of a risers system in the time domain combined with a probabilistic analysis is very cpu consuming. Therefore an approximate method applying response and capacity surfaces in combination with the analytical approximative reliability method FORM is used. An engineering approach was taken regarding the wave loading, where a regular wave with an associated period is applied. Bending failure at the end termination is addressed for the mud jumper. The major load contribution in this case is wave loading and vessel motion. The results show that stiffness of the bending stiffener, standoff position and wave height are the most important parameters contributing to the probability of failure. Tensile failure of the armoring layers is investigated for the gas export riser. For this failure mode environmental loads give only a minor contribution to the probability of failure.

• OSTI ID: 398027
• Report Number(s): CONF-940409--; ISBN 1-880653-10-9
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
DESIGN
FAILURE MODE ANALYSIS
MARINE RISERS
OFFSHORE PLATFORMS
RESPONSE FUNCTIONS
WATER CURRENTS
WAVE FORCES