Dynamic response of a steel catenary riser at touch-down zone

Abstract

This paper introduces a numerical model for analysing the dynamic response and fatigue damage of a global steel catenary riser (SCR) at the touch-down zone (TDZ). The model incorporates an innovative pipe-soil interaction model based on a new effective-stress framework to evaluate the changing soil strength induced by the cyclic motion of the SCR, thereby allowing for a more accurate assessment of the effects of soil remoulding and trenching on the dynamic responses of the SCR. The global SCR model is implemented in a commercial finite element software – ABAQUS, with the pipe-soil interaction model integrated through a user-defined element subroutine. A comprehensive series of time-domain simulations is conducted to investigate the evolution of seabed and the subsequent development of trenching along the seabed pipeline. These simulations provide valuable insights into the structural performance of the SCR at the TDZ. Additionally, this research explores the effects of water entrainment, changing seabed strength & stiffness, and the heaving motion of the floater on the fatigue damage of the global SCR. Understanding these factors is essential for obtaining an extensive understanding of the SCR's behaviour in the TDZ. The findings provide significant insights that can be leveraged to optimise existing design practices and enhance the efficiency and safety of offshore infrastructure.