Steel Catenary Risers (SCRs) are still one of the main components in development of oil and gas fields in deep waters. Riser-soil interaction in touch down zone, where the riser is in close cyclic interaction with seabed, plays an important role in fatigue design of SCRs. Linear soil models are still widely used in structural modelling for fatigue design of SCRs, however, these days nonlinear riser-soil interaction models are also available for advanced riser structural response analysis. Time-history analysis is the most preferred approach for an accurate estimation for dynamic response of SCR under randomly generated waves. Dynamic time-history analyses are usually time consuming and therefore in real projects it is usually aimed to minimize the computational efforts by minimizing the number of random realisations or even the simulation length for each random seed. This paper investigates effects of the simulation length in total induced fatigue damage in touch down zone (TDZ) of SCR using linear and nonlinear riser-soil interaction models. Statistical characteristics of the responses under different randomly generated waves are discussed in detail and they are interpreted as a result of soil trench development underneath the riser.
Atmaram Muraleedharan and Mehrdad Kimiaei
Keywords: Steel Catenary Risers, Fatigue design, Soil-structure interaction, Random Waves, Nonlinear Soil Model, Riser Dynamics
Publisher: DFI