Lifting of horizontal subsea pipeline with diverse lifting points in waves: Hydrodynamic analysis

Leveraging insights gleaned from practical marine engineering operations involving the lifting of horizontal pipelines, the subsea pipeline is conceptually disintegrated into a lumped mass parameter model. A new lifting mechanical model of pipeline suspension section based on the nonlinear beam theory is proposed and solved by simplified deformation equations of large deflection beams. Hydrodynamic analysis frameworks tailored for the vertical elevation of the horizontal pipeline at distinct locations are established. Parameters, such as effective tension, bending moment curvature, and von Mises stress, in the longitudinal direction at various lifting points are meticulously ascertained, alongside other hydrodynamic characteristics. Comparative evaluations are undertaken to discern alterations in the pipeline's configuration at diverse lifting sites. This elucidates the hydrodynamic intricacies accompanying the lifting of a horizontal subsea pipeline at varied elevation points. The introduction of additional lifting points engenders modifications in the force constraint conditions of the lifted pipeline, thereby constraining the axial expansion and contraction of the pipeline. Consequently, fluctuations in the transmission patterns of effective tension along the pipeline's longitudinal direction are observed.