An Energy-Based Approach for Jack-Up Going-on-Location Workability Assessment
J.T.J. Rigter (TU Delft - Mechanical Engineering)
J.S. Hoving – Mentor (TU Delft - Civil Engineering & Geosciences)
A. Metrikine – Graduation committee member (TU Delft - Civil Engineering & Geosciences)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
Going-on-Location (GoL) is a critical phase in jack-up vessel operations, during which the unit transitions from a free-floating condition to seabed support. During touchdown, the spudcans may experience short-duration, high-magnitude impact forces due to the coupled effects of wave-induced vessel motions, nonlinear soil-spudcan contact, and leg deformation. Current GoL workability assessments rely on detailed time-domain simulations to determine impact forces, structural unity checks, and allowable sea states. Although these methods provide a physics-based basis for operational decision-making, they are computationally demanding and mainly describe simulation outcomes rather than the underlying relation between vessel motion and touchdown severity.
This thesis investigates whether the global mechanical energy response of a jack-up vessel can be used as a physically interpretable indicator for touchdown severity and GoL workability assessment. An energy formulation is developed within an existing time-domain GoL simulation framework and verified using energy and power balance relations. The method is applied to transient impact simulations with seabed contact enabled and to free-floating steady-state
simulations in which seabed contact is disabled.
The results show that global mechanical energy provides useful physical interpretation, but does not directly predict impact severity. Critical wave realisations do not exhibit a consistent pre-impact energy level, energy build-up, or common energy peak. Instead, elevated periods in the free-floating global mechanical energy response are most relevant when they occur within the
same time window as the touchdown interval identified in the corresponding impact simulation. Three-hour free-floating simulations can characterise the timing, magnitude, and persistence of these elevated energy periods, but do not provide a consistent threshold between allowable and non-allowable GoL cases.
It is concluded that global mechanical energy should not be used as a standalone workability criterion. Its main value lies in identifying potentially critical response periods and interpreting touchdown behaviour relative to seabed contact. Future work should focus on near-touchdown and initial-contact simulations to relate energy transfer more directly to impact magnitude, while RAO-based reconstruction of the free-floating energy response could be investigated as an efficient screening method.