Investigation of the complex dynamics of float-over deck installation based on a coupled heave-roll-pitch impact model

Abstract

This paper describes an efficient methodology for analysing the dynamics of float-over deck installation, particularly arising from the wave-induced impacts between multiple structures. A coupled heave-roll-pitch impact model is developed in the time-domain to analyse the complex impact behaviour associated with float-over deck installations. The resulting time-domain model is very efficient since the time-consuming convolution terms are replaced by state-space models. The shock absorbers known as Leg Mating Units (LMUs) at the deck-to-substructure (DTS) connections, and Deck Support Units (DSUs) at the deck-to-barge (DTB) connections, are modelled as spring-damper systems with limited load capacities. By considering the coupled heave-roll-pitch motions of the float-over system, the resulting impact model is applied to analyse the complex vertical interactions between the deck and barge and between the deck and substructure at both the 0% and 100% load transfer stages. LMU/DSU impacts and DTS/DTB impacts are analysed here. In addition, the effects of varying wave excitations are investigated based on the coupled impact model.