ABSTRACT

This study focuses on the development and verification of integrated simulation framework for offshore operations using multiple offshore cranes. The framework includes physics engine based on multibody dynamics theorems and various external forces including wave, wind, current, and mooring loads in ocean environment. It also contains scenario manager to express sequence of offshore operations, integrators based on various numerical integration theorems, and static analysis calculator to find initial positions before starting a simulation. Using the framework, this study simulates an operation of pile installation using two offshore cranes and verifies the framework by comparing its results with the data from model test.

INTRODUCTION
Background

Offshore cranes are essential for offshore operations involving heavy equipment such as the installation of offshore plants and subsea equipment. As offshore operations take place in extreme environments, the weight of the equipment targeted at sea operations is increasing. Thus, to overcome this, operations may be carried out using large offshore crane or multiple offshore cranes as shown in Fig. 1.

Large offshore cranes are advantageous in that they can operate by using one offshore crane, but they are influenced by the movement conditions of the offshore crane and the seabed conditions of the offshore installation for mooring. Therefore, if it is difficult to perform an operation with a large offshore crane, it is necessary to perform a combination operation using several smaller offshore cranes. In the case of combination operation using multiple offshore cranes, there is a need to synchronize the operation of two or more cranes, which reduces the safety of the operation compared to using one offshore crane. Therefore, we must perform an analysis to confirm the stability of the operation in advance.

In this paper, we developed a prototype of an integrated framework for evaluating and verifying stability in preparation for offshore operation using multiple cranes. The developed prototype confirms the problems that may happen in the offshore operation process using multiple crane such as crane collision, disconnections of wire rope due to excessive dynamic load, and position fixation of crane barge due to mooring design error. To apply various offshore tasks in the future, the framework extensibility is considered. To this end, a framework is designed to expand and reduce functions using a plug-in model.

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