Block turnover simulation considering the interferences between the block and wire ropes in shipbuilding

Abstract

Abstract Ship and offshore plants are constructed with cranes on the dock by joining several blocks, which are basic units for design and production in shipbuilding. In the joining process, the erection and turnover operation of a block can cause interference between the block and the wire ropes on the cranes. To identify such a possibility in advance, lifting simulation, which is a kind of dynamic simulation, can be used based on multibody system dynamics. At this time, it is necessary to calculate the contact forces exerted on the block because the block can be damaged or structurally deformed if the contact forces become larger than the allowable value. However, if the lifting simulation is performed with the traditional wire rope model modeled by an incompressible spring, it is difficult to check whether the block and the wire ropes interfere with each other, and to calculate the contact forces exerted, if any. To perform a realistic lifting simulation, a wire rope model that takes interference into consideration is adopted in this study. In addition, a contact algorithm that consists of four steps is proposed to check contacts and to calculate the contact forces. First, the Moller algorithm, which is generally known as the fastest algorithm for triangle-ray intersection, is applied to detect the contacts. Second, the contacted wire rope is divided to cope with the contacts. Third, the contact forces are calculated with the sum of the tensions in the wire rope segments including a contact point. To verify the efficiency and applicability of the proposed method, it is applied to block turnover simulation. It can be seen that the contacts can be accurately checked, and the corresponding contact forces can be calculated if there are contacts between the block and the wire ropes on the crane.