Investigation on Offshore Riser Structure Span Design

초록

Offshore risers are common components used in offshore platforms. Being vertically located, risers are weakly exposed to environment. There are many design considerations in riser design. Among them, the vortex shedding is one of the most important factors. If the vortex shedding occurs, it could also cause a fatigue failer. The riser span between clamps should be decided to avoid the vortex ocillations. The current, i.e. steady flow, is the main contribution factor in vortex generation. The cyclic load caused by wave also contributes to riser fatigue failer. Therefore, the both current and wave, affect to riser fatigue failure. The free span length calculated from vortex shedding analysis are compared with those from fatigue analysis. The riser models in the study are consisted of dual pipes having inner and outer pipes. The beam element modelling is applied to convert the dual risers to equivalent condition.