Session: 06-11-01 Ocean Engineering Technology I

Paper Number: 78400

78400 - Dynamic Property of a Floating Multi-Body System for Dual Barge Float-Over Operation With a Mechanical TLS (Topside Lifting System) 

TLS (Topsides Lifting System) utilization is a modern fast lifting technology developed for offshore platform installation and decommissioning operation. The positive prospects have been seen from its sound and efficient performance at the offshore operation. Taking the catamaran float-over operation with an innovated TLS system as the study case, a mechanical and hydrodynamic coupled multi-body model both in frequency and time domain is established to analyze the dynamic properties of the new operation mode.

The targeting TLS system consists of several sets of lifting beams that can move along the rail in X and Y directions on two specially designed vessels. The gripping teeth at the interface are used to sea fasten the topside to lifting beams. In present study, each lifting beam is modeled as a rigid body with X and Y degree of freedom relative to the barge. Mechanical couplings between the barge, lifting beams and the topside are all modeled as spring-damper systems with a designed stiffness and damping coefficient to simulate the flexible connections.

Compared to traditional single barge float-over technology, the coupled catamaran system consists of dual barge, the lifting beams and the topside. The dynamic characteristics will be more complex because the flexible mechanical and hydrodynamic couplings in system. The hydrodynamic coupling effects in frequency domain between two barges are analyzed first. The eigen value analysis is also carried out to identify the flexible connections induced new eigen modes of the coupled multi-body system. The effects of flexible mechanical couplings on the motions of barges and topside and the coupling forces acted on lifting beams are investigated under different sea states. The results indicate that the larger motions of barge in certain wave conditions are observed when a flexible mechanical coupling is considered. The analyzed dynamic characteristics provide an initial cognition reference of the new operation system and help with the system design especially for TLS. The established multi-body model can also be used for the construction scheme optimization and the weather window determination.

Presenting Author: Shujie Zhao Ocean University of China

Authors:

Shujie Zhao Ocean University of China
Zhen Gao Norwegian University of Science and Technology
Dejiang Li Yantai CIMC Ocean Engineering Co., ltd
Xun Meng Ocean University of China