Spectral fatigue analysis of shallow water jacket platforms
- University College London (United Kingdom). Dept. of Mechanical Engineering
- WS Atkins Consultant Ltd., Epsom (United Kingdom)
- British Gas PLC, Newcastle upon Tyne (United Kingdom)
The spectral analysis approach is a very elegant and computationally efficient method of analyzing the fatigue life of offshore jacket platforms. The primary limitation of the approach is that it assumes linearity of both the structural system and the wave-loading mechanism. The approach is now widely used for the analysis of deepwater, dynamically responsive platforms where nonlinearities are usually not serious. There are also advantages associated with using the approach for shallow water platforms although nonlinearities then become significant, particularly the wave-loading mechanism. In order to verify the new approach, a time series analysis, including wave-loading nonlinearities, has been adopted to obtain a reference fatigue life. The sea surface elevation spectrum has been decomposed into a set of equivalent harmonic components. The water particle velocities and accelerations were then individually evaluated and the appropriate (Morison`s) wave loading was computed for each time step in the sea surface time history. The structural stress response time history was then calculated, from which a fatigue life estimate was obtained. This paper presents the results obtained using this new approach, as well as comparative results obtained using the deterministic, spectral, and time domain approaches applied with a representative sea state. The results show that the deterministic-spectral method has a considerable amount of potential, especially for new design work where weight savings and/or increased confidence levels may be achieved.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 395379
- Journal Information:
- Journal of Offshore Mechanics and Arctic Engineering, Journal Name: Journal of Offshore Mechanics and Arctic Engineering Journal Issue: 3 Vol. 118; ISSN 0892-7219; ISSN JMOEEX
- Country of Publication:
- United States
- Language:
- English
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