Spectral fatigue analysis of jacket platform under wave load equipped with viscous damper

• Published in: Journal of marine science and technology 2019-09, Vol.24 (3), p.855-870
• Main Authors: Janbazi Rokni, Hossein, Tabeshpour, Mohammad Reza
• Format: Article
• Language: English
• Subjects: Analysis; Automotive Engineering; Computer software; Crack propagation; Earthquake damage; Earthquake dampers; Earthquakes; Energy dissipation; Engineering; Engineering Design; Engineering Fluid Dynamics; Fatigue; Fatigue failure; Fatigue life; Fatigue testing machines; Flow velocity; Forces (mechanics); Friction; Investigations; Load; Loads (forces); Materials; Mechanical Engineering; Natural gas reserves; Offshore; Offshore drilling rigs; Offshore Engineering; Offshore platforms; Oil reserves; Original Article; Piled platforms; Probability theory; Rehabilitation; Seismic activity; Spectra; Spectral density function; Spectral methods; Stress concentration; Time domain analysis; Wave forces
• ISSN: 0948-4280; 1437-8213
• DOI: 10.1007/s00773-018-0592-9

Offshore jacket platforms are exposed to environmental loads such as wind, wave, current, and earthquake throughout the lifetime of operation. Due to dynamic and periodic nature and fatigue phenomenon in the structure, wave forces are the most important loads among others. There are diverse methods to explore the fatigue life of jackets, including deterministic, spectral, and time domain analysis. Among these methods, spectral method is a reliable method, which considers the random nature of sea waves in fatigue analysis. In the current study, a spectral method is introduced for assessment and rehabilitation of jacket platform structure. To this end, a computer program has been developed, meanwhile, probability spectral density functions of displacement and stress are calculated in each joint of jacket elements. Furthermore, using S – N curve approach, cumulative fatigue damage in critical members of an example jacket is obtained. Finally, several configurations of viscous dampers are applied to jacket, and damage and fatigue lifetime are discussed with and without dampers. Consequently, the best arrangement of dampers is achieved. Results indicate the best cumulative fatigue damage with dampers which was about 0.01 times of cumulative fatigue damage without a damper.