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http://dx.doi.org/10.3744/SNAK.2010.47.6.813

Fatigue Damage Combination for Spread Mooring System under Stationary Random Process with Bimodal Spectrum Characteristics  

Lim, Yu-Chang (Dept., of Naval Architecture & Ocean Engineering, Inha University)
Kim, Kyung-Su (Dept., of Naval Architecture & Ocean Engineering, Inha University)
Choung, Joon-Mo (Dept., of Naval Architecture & Ocean Engineering, Inha University)
Publication Information
Journal of the Society of Naval Architects of Korea / v.47, no.6, 2010 , pp. 813-820 More about this Journal
Abstract
The spread mooring system for FPSO is developed to explore deep sea area, in which swell is dominant. It is known that the tension response of mooring lines in this sea area shows bimodal spectrum. Assuming normal distribution of tension profile and Rayleigh distribution of tension amplitude, the power spectral density function (PSD) of the mooring tension under the bimodal stationary random process is applied for the calculation of spectrum fatigue. Three popular methods, which are simple summation method, combined spectrum method and Jioa-Moan method, are used to combine fatigue damages from bimodal spectrum characteristics. Each damage value is compared with damage using Rainflow Cycle Counting (RCC) method which is believed to be close to exact solution. Vanmarcke' parameter and RMS(Root Mean Square) ratio are employed to assess relative damage variations between from RCC method and from three combination methods. Finally the most reliable fatigue damage combining method for spread mooring system is suggested.
Keywords
Spread mooring system; Spectrum fatigue assessment; Power spectral density; Bimodal stationary random process; Rainflow Cycle Counting;
Citations & Related Records
Times Cited By KSCI : 2  (Citation Analysis)
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