This study deals with two issues of dynamic analysis for ships and offshore structures. One is collision detection and response calculation for the LPG tank erection lifted by the floating crane. An LPG tank has too many meshes which are not enclosed. Therefore, space partitioning known as boundary volume hierarchies, and exclusion boxes are applied to decrease computing time. The other issue is a structural analysis of the thin plate block considering the flexibility. Flexible multibody dynamics are used to analyze the deformation during the block lifting operation.
In shipbuilding industry, the ships and offshore structures are built by assembling several pieces of blocks one by one. The main operations are composed of lifting, moving, and lowering the block by using the several kinds of cranes such as a gantry crane and a floating crane. Before conducting the operation, the owner or the classification society sometimes requires the safety evaluation. In this case, the dynamic analysis program is used to check the motions and tensions between the block and the crane within the safety criteria.
Meanwhile, two issues related to dynamic analysis were not solved until now. One is collision detection and response calculation. A collision between the lifted block and substructure or between the lifted module and the deck might happen during the erection or installation. Because the block and substructure model usually have many meshes, it takes much time to detect collision between them. The other issue is dynamic analysis considering flexibility of the lifting block during the operations. The block usually experiences deformation because the limited number of the lifting points are used to lift the block. Besides, the forces acting on the lifting points continuously change with time due to the environmental loads.
This study proposed collision detection and response algorithms to solve the first issue. We also adopted flexible multibody system dynamics to solve the second issue. The following sections will explain the related theoretical backgrounds in detail.
