Upper Ball Joint Force Variations due to Riser Tensioner and Vessel Motions—Part II: Analysis and Computer Simulation

Part 2 of a study of upper ball joint force variations due to riser tensioner and vessel motions. An analysis of the variation of forces acting on the upper ball joint of a riser string due to the drill ship motion and riser tensioner dynamic has been conducted. The analysis includes the effect of breakaway torque on the tensioner sheaves while assuming vessel and upper ball joint motion to be independent. General equation for the tensioner cable forces and for the forces exerted on the riser upper ball joint by the ship joint-tensioner system derived in Part I are solved. The variation in the tensioner cable forces is compared to data generated in field operation