Dynamic Response of a Floating Rigid-Plastic Box

A method is presented to determine the deformations of a rigid-plastic box structure that floats on the surface of a fluid and contains an internal, elastically-supported mass. This model is a simple representation of a surface vessel in which plastic deformations resulting from an underwater shock greatly exceed the elastic deformations. The method is applied to the case of symmetric initial velocity distribution, excluding buoyancy effects. Numerical solutions for two simple initial velocities are obtained for the complete range of a significant parameter. The results indicate that when substantial plastic deformations occur, the solution consists of many phases, in each of which a certain group of plastic hinges is active. If the number of plastic hinges (and degrees of freedom) becomes large, the number of phases in a solution may become excessively large, and the conditions separating them are complicated.