The Jackup Durability Problem

Abstract

ABSTRACT This paper summarizes the more salient results of an on-going study of elevated jack-up rig durability carried out by the Workgroup Offshore Technology (WOT) of the Delft University of Technology. Significant discoveries, critical in a design or performance analysis, are presented here. The references include all the reports produced in this study so far. It is concluded that many common approaches used with jack-ups today have serious shortcomings and that many more or less accepted design approaches fail when applied to elevated jack-ups in deeper water. This can explain the disparity of field data and results found using various analysis approaches on one and the same jack-up rig. Elevated jack-up platforms demonstrate significant nonlinearities in their overall dynamic structural behavior. The most important of these involve interactions of the legs with: the sea bed via a spudcan, the deck via the deck-leg clamping system, and the sea itself: waves and currents acting on the moving structure. Inclusion of all these nonlinearities in a design production computer simulations is uneconomical; instead, these can be checked against a benchmark, complete simulation to be developed within this project.