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This paper proposes a fatigue reliability assessment method of offshore steel catenary risers (SCRs) caused by internal slug flow. Offshore risers subject to slug flow are modeled first by employing a finite element method scheme. Subsequently, a combination of Kriging metamodel and Monte Carlo simulation (MCS) is established to assess the fatigue reliability of SCRs conveying internal slug flow. An explanatory example of a 16‐inch SCR is presented to validate the performance of the proposed method and the results indicate that the failure rates of the SCR are significantly affected by the frequency of slug flow. Moreover, the accuracy and feasibility of the present method are validated by a comprehensive comparison with the existing experiments and numerical results. The present method contributes to the design and maintenance of offshore risers with internal slug flow. [ABSTRACT FROM AUTHOR]

A nonuniform distribution of internal flow along the offshore riser can lead to transient in-plane excitation. To predict the global riser response due to slug flow by nonlinear time domain analyses, a finite element method is developed in this study by combining the absolute nodal coordinate formula (ANCF) and arbitrary Lagrange-Eulerian (ALE) description. This proposed method has the capacity to effectively simulate both the nonuniform gravity distribution of slug flow and geometric nonlinearity of the riser. The nodal position and slope vectors described in the global coordinate system avoid the complex coordinate transformation of the elements while the internal fluid is effectively integrated into the framework. After the accuracy of the proposed program is verified, a kind of steep wave riser (SWR) with internal flow is taken as an example to discuss the effect of slug flow. The results show that slug flow can result in large local deformations and lead to variable pattern changes in the bending moment. • A modeling method based on ALE-ANCF is proposed to simulate oscillations of offshore risers conveying the slug flow. • This formulation effectively describes the slug-flow and avoids the complex coordinate transformation. • The methodology is suitable for the slug-flow-riser interaction problem undergoing large deformations. • The effect of slug-flow on the global response is analysed for a steep wave riser. • Large fluctuation amplitudes of the global bending moment are observed when considering the slug-flow load. [ABSTRACT FROM AUTHOR]