Cyclic plastic deformation of overbend pipe during deepwater S-lay operation

•We carried out a large pipe-stinger model test to investigate the dynamic roller force.•We build a 3D nonlinear finite element model to observe the pipe cyclic plastic deformation.•We obtained the cyclic plastic stress time history of overbend pipe during its sliding downward the stinger process.

In deepwater S-lay operations, the combined influences of stinger curvature, axial tension and roller support force can induce very large plastic deformation in the pipe. Dynamic loads from vessel motion and pipe sliding down the stinger lead the cyclic plastic deformation. This paper investigates the cyclic plastic stress history of the overbend pipe subjected to the dynamic pipelaying loading. The dynamic roller support forces are obtained through an innovative large scale hybrid substructure experiment constructed to simulate the pipe-stinger impact behavior. The measured roller forces are used to verify a 3D finite element analysis results developed with ABAQUS/Standard to observe the dynamic pipe stress history. The results confirm that the roller support can induce stress concentration in the pipe and the combined dynamic pipelaying loadings can cause extensive cyclic plastic deformation.