Steel Catenary Risers (SCRs) are commonly used in the offshore industry. Strength and fatigue performance of SCRs due to waves, currents and vessel motions is typically calculated using time domain dynamic analysis. Strength analysis may involve a large number of load cases for different environments, riser conditions and vessel configurations. Fatigue analysis may involve computation of riser response for hundreds of fatigue sea-states. It is very important for project schedule and cost that the analysis software used is both accurate and computer efficient. This paper presents RodDyn as an alternative time domain analysis tool for SCR strength and fatigue analysis.
RodDyn is a finite element program for dynamic analysis of single-pipe risers. Several publications on this program are available in the literature. The results of dynamic analysis of an SCR for strength and fatigue from RodDyn are compared against the results from ABAQUS. ABAQUS is a general finite element program that has been widely used in the offshore exploration and production industry and has been considered one of the standard finite element programs. Riser dynamic analysis uses time series of vessel motions due to metocean environments at an oblique angle to the plane of the SCR. Von Mises stress per API RP 2RD, strength checks per API STD 2RD and fatigue damage along the riser are presented for both RodDyn and ABAQUS. Time series of effective tension and bending moments at selected locations on the riser are also compared.
The main advantage of using RodDyn for riser analysis is the speed of computation. This paper shows that RodDyn can deliver significant gains in computational speed compared to standard riser analysis software programs without sacrificing accuracy of the computed results.