EFFECT OF SEABED SOIL STIFFNESS ON DYNAMIC RESPONSE OF A STEEL CATENARY RISER AT TOUCHDOWN POINT

The dynamic response at touchdown points (TDP) is presented under different soil stiffness and the motion of a floating structure. The sag bend and the flowline of the steel catenary riser (SCR) have been simulated with a slender beam and an elastic foundation beam model based on the assumption of a large deformation in bending and small extension. In this approach, the SCR’s governing equation is established and solved using nonlinear FEM, Newmark-β method is employed for time-domain integration. The sea bottom is modeled by a spring-damping system in the dynamic simulation. The dynamic response and stress at the TDP under linear wave loads are given considering boundary conditions at the top of SCR. Theoretical results are compared with numerical solutions. It is shown that the level of soil stiffness used in SCR analysis is too high then the predicted fatigue life, that the extreme bending stress at the TDP is induced by the vertical motion of SCR.