Response of steel catenary risers on hysteretic non-linear seabed

• The non-linear riser-seabed interaction has a vital influence on fatigue performance
• We examined it by implementing an advanced seabed model into the seabed in ABAQUS
• The riser stress profile under cyclic loading and non-linear seabed response was studied
• We propose new methodologies for riser fatigue analysis in presence of non-linear seabed
• The riser dynamics was found positively contributing to fatigue life

The methodologies recommended by existing codes and standards for design of steel catenary risers are considering linear springs in the seabed while it is publicly accepted that the non-linear riser-seabed interaction can have vital influence on stress variation in touchdown area and consequently fatigue performance during the cyclic motions of the riser as the latter is excited by vessel motions under environmental loads. In this study an advanced hysteretic non-linear riser-seabed interaction model has been implemented into the seabed enabling the automatic simulation of different stiffness in the seabed response through the touchdown zone and gradual embedment of riser. Then the impacts of this model on fatigue calculation procedure and fatigue performance in touchdown area has been studied.