Wave motion analysis plays a crucial role in ensuring accurate and reliable fatigue life predictions for deepwater risers. This study investigates how different modeling approaches and key parameters affect wave-induced motion fatigue damage, using representative metocean conditions typically found in ultra-deepwater risers connected to floating units. Both irregular and regular wave methodologies are considered through time-domain dynamic analysis.

Irregular sea states are modeled using the JONSWAP spectrum, while regular waves follow Airy wave theory. This study also explores the influence of specific wave parameters on fatigue assessments, including wave seed numbers for stochastic realizations, individual wave components, and critical environmental and operational factors that affect wave–riser interactions. A range of riser configurations are analyzed to capture variations in hydrodynamic input and their impact on fatigue loading.

Different strategies are applied to identify critical cases. While irregular wave analysis requires longer simulation times, regular wave methods offer faster alternatives. This study compares their accuracy and relevance for different scenarios. Results show that the choice of parameters and approach significantly affects fatigue predictions, with measurable correlations observed under complex ocean conditions.

Based on these findings, this study offers practical recommendations for selecting appropriate analysis methods depending on riser configuration and wave characteristics. These insights aim to support offshore engineers in improving the reliability of riser design and enhancing the resilience of deepwater systems.