3D Frequency Domain Analysis of Offshore Structures

This paper reports the application of three-dimensional (3D) frequency domain computational tools to the dynamic analysis of offshore structure systems. Previous applications of 3D frequency analysis by the present authors in the areas of TLP tether and jack-up analysis are summarised. Results are presented here for a new area of application, namely a deep-water multi-line steep-S flexible riser configuration. The results are compared with time domain calculations and, in general, excellent agreement is reported. A nonlinear static option, which permits linear dynamic motions about a nonlinear static position, is outlined as an efficient extension of the basic frequency domain method. The present work addresses an area where frequency domain analysis has not previously been systematically exploited, and indicates excellent potential for future innovative applications.