Structural reliability analysis of offshore jackets for system-level fatigue design

• Published in: Structural safety Vol. 97; p. 102220
• Main Authors: Mendoza, Jorge, Nielsen, Jannie S., Sørensen, John D., Köhler, Jochen
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.07.2022; Elsevier BV
• Subjects: Algorithms; Component reliability; Computer applications; Computing time; Design; Design techniques; Fatigue; Fatigue failure; Fatigue limit; Jackets; Lattice design; Limit states; Materials fatigue; Offshore platforms; Redundancy; Reliability analysis; Reliability engineering; Reliability-based design; Statistical analysis; Structural reliability; System reliability; System-level design; Upper bounds; Weight reduction; Welded joints; Wind power; Fatigue; Reliability-based design; System reliability; Jackets; System-level design
• ISSN: 0167-4730; 1879-3355
• DOI: 10.1016/j.strusafe.2022.102220

Lattice systems such as offshore jackets and towers are weight-efficient support structures for wind energy and oil and gas units. Nevertheless, their light-weight is achieved at the expense of increasing their proneness to fatigue failure, due to their many welded connections. Consequently, special attention is to be dedicated to the design of the fatigue hot spots. System-level fatigue design methods aim at calibrating the reliability of the fatigue components to achieve a desired target system reliability. These methods rely on the accurate assessment of the system probability of failure, which is computationally demanding due to the statistical dependence among fatigue limit states and the large number of possible deterioration states that need to be taken into account. In the present paper, we develop a novel approach, called the truncation algorithm, to estimate lower and upper bounds of the system reliability due to extreme environmental and fatigue limit states within feasible computational time. The proposed approach is applied to assessing existing system-level fatigue design methods and to study system effects, such as the effects of redundancy and the correlation among fatigue limit states on the system reliability. •A novel method is proposed to assess bounds of the system reliability of jackets.•System effects are studied for common bracing systems.•The safety level associated with two system-level fatigue design methods is studied.•Complex deterioration states significantly contribute to the probability of failure.