AN ENHANCED EQUATION FOR VIBRATION PREDICTION OF NEW TYPES OF SHIPS

Sa？etak A simplified approach developed to evaluate the vibration levels of complex structures such as passenger and similar ships with large shell and deck openings and extended superstructures is here presented. The final objective is to give an useful tool to ship designers, to establish since the first design stage the dynamic response of the ship with sufficient precision. This approach is based on the assumption that the ship hull can be represented as a non uniform section beam. The propeller excitations in terms of pressure pulses and shaft line moments and forces are introduced. To take into account this exciting source in the early design stage a statistical formula for dynamic excitation of propeller was developed. Furthermore the superimposition of local effects has been performed with the use of an analytical formula. The local effect due to the different space topologies such as cabins, public spaces, technical and machinery areas has been taken into account. The transversal beams, longitudinal girders, stiffeners and pillars as supported structural elements are considered in the vibration local response. The reliability of the results obtained using the formula has been improved with more precise results obtained by FEM analysis. The calculated vibration response has been verified and compared to vibration measurements performed on board of ships