Vertical dynamics of marine risers.

A study of the vertical dynamics of marine riser load systems was performed to determine the amplitude of dynamic forces and displacements caused by heave action. The analysis predicts circumstances under which slackening or compression, and subsequent failure of a riser can occur. Results show that a suitably designed heave compensator can reduce the dynamic stress amplitude to acceptable values under all operating modes including hangoff, by increasing compliance at the riser vessel interface. Finally, recommendations for the design of heave compensation equipment intended to limit the dynamic force amplitude on riser load systems hanging in deeper waters and harsher environments are presented. (A)