Note: This study is part of a broader project “Seafloor Interaction With Steel Catenary Risers ” (MMS Project 510).
More detailed analysis of risers can be conducted using non-linear finite element analysis programs. Most riser analysis codes use either rigid or linear elastic contact surfaces to simulate the seabed, which model vertical soil resistance to pipe penetration, horizontal friction resistance and axial friction resistance (Bridge et al., 2003). Until recently most analysis was conducted assuming the seabed is rigid or that it exhibits a linear stiffness. A rigid surface generally gives a conservative result since it is unyielding, while the linear elastic surface is a better approximation of a seabed.
This study concentrates on conducting numerical studies to understand basic interaction mechanisms and on developing a simplified model for a seafloor interaction with steel catenary risers within the touchdown zone. The response of the seafloor to SCR movements will be studied to formulate a proper boundary condition at the seafloor touchdown zone for structural analysis of a riser subjected to vertical loading representing the vessel motion and seabed current. The relative importance of various seafloor and loading conditions on bending stresses of the riser pipe resting on nonlinear spring supports will also be investigated. This research concentrates on only vertical motions of riser pipe, although axial and lateral motions may have to be considered in the future.