In this study, docking operation during float-over installation on jacket structure is investigated. Docking is a very sensitive operation, as the allowed motion responses of DTV(Deck Transportation Vessel) are strictly limited for successful operation when DTV enters slot of jacket to install Topsides on the jacket structure by float-over. Therefore, it is important to assess DTV's motion responses accurately for the designed configuration with mooring lines and fenders in combined environmental conditions. Assessments of docking operation using the commercial software, ANSYS AQWA, were carried out for various environmental conditions, after a series of validations through the comparisons with previous results of analysis and model test. Results of parametric studies are presented in the paper, which are to show the effects of gap between DTV and fender, fender stiffness, mooring line stiffness and random seed for realization of irregular waves.
There are high interests in float-over installation which can install heavy structure at one time, especially as topsides facilities are becoming larger and heavier. Key issues during docking that DTV enters slot of fixed (or floating) structure to install topsides on it are motions at receptacle points. For successful mating, horizontal motions are to be within the capture radii of the designed receptacles and stabbing cones. Vertical motions are also to be checked for the design of mating aids. Other important factors such as fenders and moorings are to be assessed and considered as well. It needs cautions in these assessments, as physical values dealt with are usually smaller and more sensitive than typical seakeeping analysis. Analysis of the docking stage during float-over installation on jacket structure are introduced in this paper with validation and parametric studies.
Fig. 1 shows a snap shot of float-over installation of topsides on jacket structure. Among the entire float-over procedures, this paper focuses on a docking problem that DTV enters slot of jacket and waits for mating.