A parametric study for the structural behaviour of a lightweight deck

Artikel i vetenskaplig tidskrift, 2004

Lightweight structures are increasingly used for high-speed ships. Research of fatigue and stability of the highly stressed thin plate structures is an ongoing activity, which produces valuable information for the structural engineers. One topic that should be an integrated part of these studies is the dynamic behaviour of lightweight deck structures. When the deck structures are made extremely lightweight, the natural frequencies of the structures as such may increase while the loaded decks will most likely deflect more than conventional decks do. It is then expected that the natural frequencies of the decks will decrease and new problems of vibration and damping will appear. There is concern for resonance with propeller blade frequencies but also with the wave responses of these high-speed ships. The subject of this paper is to study the static and dynamic behaviour of a lightweight ship deck. A theoretical model was made in order to study the interaction between the car and the deck. The model indicates that the car chassis is a significant part of the problem and influences the solution. A finite element model of the ship deck was generated and special parameters, such as material of the panels, numbers and locations of loaded cars were studied. The speed of running cars on the deck during loading and the frequencies of the propeller excitation were varied in order to understand their influences on the structural response. Based on the results from finite element analysis obtained, it is shown how a conventional steel structure is improved by introducing lightweight material. The structural behaviour is significantly influenced from both a static and dynamic point of view.