An offshore support vessel (OSV) is a ship that supports exploration, development, and production activities in the offshore industry. Recently, industrial demand for OSVs has increased due to a large number of offshore field development projects worldwide. One of the main functions of an OSV is heavy lifting such as subsea equipment installations in offshore oil or gas fields using crane. Therefore, predicting dynamic loads in various operation conditions is one of the crucial points in the lifting operation of an OSV. To do this, crane-lifting simulation needs to precede real operation to verify the safety of the lifting operation. Most simulation tools use a rigid body model for crane-lifting simulation. However, in real cases, some heavy loaded components such as crane boom might be deformed due to their own weight and the weight of the lifted object. The deformation can change during the lifting operation because ship motion induced by ocean waves and winds can affect the overall behavior of the OSV. This study derives equations for the motion of a multibody system using a flexible body model for the crane boom based on finite element formulation to analyze the behavior of the system, dynamic loads, and the deformation of the crane boom under various ocean conditions. Motion equations were solved with fourth-order Runge-Kutta method. Our results showed that flexible body models had bigger dynamic amplification factors than rigid body models in all cases, indicating that the flexibility of the crane boom should be considered for accurate estimation of the dynamic effect on OSV lifting simulation. Finally, we can find operability of the lifting operation at given ocean conditions.

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