Abstract

Random stress produces fatigue damage due to fluctuation in the presence of high bending stresses gets enhanced and leads to the primary failure of the production composite riser. The main problems with the fatigue deterministic model are related to the fact that not all waves have the same period. The second problem is due to the assumption that all waves are regular and do not into account the stochastic nature of the marine environment. The wave data is provided on a statistical basis. Work attributed to damage related stress distribution and interaction of composite along with integral difficulties in fatigue is challenging task. Resulting flexural stress history is random in nature. The purpose of this study is to present a methodology for assessing cumulative fatigue damage using MATLAB of the deep-water composite riser. The simulation of 12 random sea states is examined for the purpose of estimation of accumulated damage. Using the recommended method by DNV-OS-C501, fatigue life of composite riser is determined for different conditions. Damage induced by stress signals of varying amplitudes is calculated using Palmgren-Miner’s rule. Total fatigue life for stress history is estimated by the summation of damage fractions. Estimation of fatigue damage over riser’s entire service life is done taking into consideration the entire expected sea area. Extreme flexural stress random fluctuations are estimated with and without currents.

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