Dynamic response of steel catenary riser using a seabed interaction under random loads

It is important to develop better understanding of the Steel Catenary Riser (SCR)-soil interaction mechanism to provide a realistic technique to predict the dynamic response and structural behaviour of the SCR in the Touchdown Zone (TDZ).This paper discusses the significance of SCR-seabed interaction in the design of SCR for deepwater applications and reports the results of an analysis of an SCR on soft clay in 910 m depth of water using the commercial code OrcaFlex for non-linear time domain simulation with a robust meshing technique. In the study reported in this paper, the vertical embedment and large lateral movements of the SCR in the TDZ were investigated. During the simulations the seabed has been modelled using a hysteretic non-linear model in vertical seabed direction, and bilinear and trilinear models in the lateral seabed direction. It has been found that the TDZ responses result in the degradation of the seabed soil stiffness due to cyclic loading. Furthermore, an improved SCR-soil interaction model, with accurate prediction of soil stiffness and riser penetration enables us to more accurately predict global riser dynamic performance in the TDZ.