Spectral Fatigue Analysis of Jacket Stuctures in Mumbai High Field

• Main Authors: S. Nallayarasu, S. Goswami, J.S. Manral, R.M. Kotresh
• Format: Article
• Language: English
• Published: SAGE Publishing 2010-09-01
• Series: International Journal of Ocean and Climate Systems
• Online Access: https://doi.org/10.1260/1759-3131.1.3-4.209

Fatigue analysis of offshore structures is an integral part of design of offshore structures and shall be carried out with suitable method of discretising the seastate. Historically, for most of the fixed offshore structures, deterministic fatigue analysis found to predict the fatigue damage reasonably well and has been in use for several decades. Fixed structures with small topsides, mostly exhibit a static response characteristics and the natural period may be in the order of less than 2 seconds. Offshore platforms with larger production capacity and deeper water depths may require specialised treatment of seastate due to their dynamic characteristics more vulnerable for fatigue damage. A spectral fatigue analysis has been performed for two different platforms in Mumbai high field (MNP and RS14) and a comparison is made with deterministic analysis. The spectral fatigue analysis indicates that the predicted fatigue life is lower than the deterministic analysis since the dynamic amplification of wave loads are treated approximately in deterministic analysis. Hence for large structures, it recommended to use spectral methods to assess the fatigue life of tubular joints.