As risers are designed for more deeper water applications, factors thatpreviously were not considered to be important in determining theresponse of the system can become important. This is especially in thedesign of ultra-deep water risers, e.g. development of deepsea miningrisers in around 5000m water depth. One such effect is the axial naturalfrequency which increases with depth and thus for deep water risercomes into the frequency zone that is excited by environmentalconditions. It influences the dynamic response of the system due towave motions, and this can be simulated via full beam elementsoftware that includes the axial stiffness. For the response under vortexshedding or VIV, industry software uses modal based methods, e.g.Shear7, these do not include any axial properties in the calculation, thusthe potential for any axial stress and motion is missing. This paperaddresses the impact of vortex shedding on riser axial resonance andperforms basic assessment for the fatigue damage that could be causeddue to the axial resonance. Reference is made to the EU funded BlueMining project for which axial mode oscillation is detected to occur.
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