Nowadays, noise and vibration problems tend to become an important part of the design process in the naval industry. Vibrations often affect the passengers comfort, but more dangerously may damage the structure, embarked merchandise and equipments. A simple way to avoid vibrations is to prevent the resonance conditions. The paper presents a study about the vibration of local structures (beam structures and stiffened panels) with application in the marine industry. The model has been implemented in FORTRAN into a numerical module and will be integrated in the near future with the LBR-5 generic stiffened structure optimization code.
Vibrations acting into the mechanical systems can cause many problems at different levels such as mechanical and performance degradation. If we include the human factor, the study of the vibration becomes extremely important. The main application of this study refers to marine field and particularly to ferries and RO-RO ships for which the vibrational comportment is often verified in the preliminary design stage process or during the structural design phase. A ferry or RO-RO ship is characterized by very large decks that may suffer from fatigue due to vibrations. The LNG's tank walls can be also affected by vibrations, but in this case we must take into account the fluid-structure interaction. Another important application connecting the marine and vehicle fields refers to the dynamics vehicle/ship-deck investigations. The experiences demonstrate that the dynamic interactions between the vehicles and the vessel deck (for example, a roll-on/roll-off RO-RO vessel with vehicle cargo) may be very different from that of static case. It was found that the vehicle cargoes can work as mass dumpers to reduce at least one mode shape response of the deck (Jia, 2004). The work presented in this paper do not treat the global vibrations of these ships and it is devoted only to local structure, such as beams, stiffened panels, their assemblies, and other connected problems.