A SIMPLIFIED METHOD TO ESTIMATE RISER FATIGUE LIFE CAUSED BY VORTEX-INDUCED RESONANCE

According to the characteristic of deepwater top tensioned riser, a simplified method for estimating fatigue life caused by vortex-induced resonance is presented. The simplified model combines the analytical solution for transverse modal vibrations and the empirical expression of VIV amplitude based on wake oscillation model. It is proved that the method can take account of the modification of vibration mode and fatigue life caused by the variety of axial tension along the riser. The critical joint of fatigue damage due to VIV is presented and the effort of flow velocity on fatigue life is also discussed. This method is simple and practical for approximate calculation of fatigue damage from VIV of slender tensioned structures in design process.