Time-domain structural analysis during block turnover and lifting using 2D flexible multibody dynamics

Abstract

Ship construction involves the assembly of several blocks on a dock. When a block is lifted using a crane, it undergoes deformation. Until now, structural analysis has been applied in a few cases to evaluate the stress on such blocks. Therefore, this study proposes an evaluation method for time-domain stress using 2D flexible multibody dynamics. We adopt the discrete Euler-Lagrange equation to achieve robustness during the numerical integration of problems that involve high stiffness. We formulate the equations of motion of 2D shell elements based on the absolute nodal coordinate formulation, which is an efficient analysis technique for nonlinear and large deformation cases. We also derive the two types of kinematic constraints (ball and fixed joints) between the rigid and shell element, which can be attached to an arbitrary point. Based on the theories, we develop the program to build models, including 2D flexible multibody dynamics and several joints, and to solve the equations of motion efficiently. As a result, it is successfully applied to the dynamic analysis of the block turnover by a gantry crane and the block lifting by a floating crane. The von-Mises stresses that change over time are compared to the maximum yield stress and analyzed according to the wave direction.