Numerical analysis of nonlinear dynamic structural behaviour of ice-loaded side-shell structures

Artikel i vetenskaplig tidskrift, 2009

This investigation examines how the nonlinear structural response of a ship side-shell structure that impacts with ice is affected by the layout/design of the structure, ice characteristics and ship speed operational conditions. The finite element (FE) method was used for nonlinear analysis and comparison of a reference side-shell structure with a topology-optimized structure. Nonlinear dynamic FE collision simulations were carried out, using the reference side-shell structure, to study how the impact with ice (having different values of damping coefficients), and the variation in ship speed operational conditions, affected the damage caused to the side-shell. In addition, the results from the comparison of the topology-optimized and reference side-shell structures showed slightly larger stresses locally in the former structure. It was concluded that it was possible to reduce the weight of the reference side-shell structure and that the objective function and optimization require more detailed investigation. The FE analyses with various damping coefficients of ice showed that, for the chosen values of the damping coefficients, there was only small influence on the dynamic nonlinear response of the reference side-shell structure. Finally, a limit value for the maximum allowed velocity in the normal direction towards a level ice belt of the reference side-shell structure was calculated to result in an elastic structural response of the side-shell. For a side-shell structure movement in the direction along a level ice, the influence of velocity on structural response was negligible due to low friction between the side-shell structure and the ice in the contact.