Stern Vibration Analysis Of A Comprehensive Rescue Ship

The comprehensive rescue ship is a new kind of auxiliary ship,which is designed for rescuing other ships in case of emergency.Considering the unique characteristic of rescue ship,more attention should be paid to the stern vibration.This article completes direct vibration analysis of a comprehensive rescue ship.Referring to the requirement of GJB/Z 1999-99,assessment of the vibration response is conducted,which can ensure that the ship will work in security and the equipment on board will operate normally.The main elements and conclusions of this thesis can be concluded as follows:(1)Mixed finite element model,with mass and stiffness distribution simulated appropriately,is established to carry out the modal analyses.The added mass and water springs' stiffness are also calculated.Then,checking of the frequency reservation is completed,which shows that the natural frequency of the hull can be staggered with the excitation.(2)Modal analyses are also carried out about deck grillages,bottom grillages and propulsive cabin.And the results show that the frequency reservation about most of the aft structures is satisfied with the specification requirements.(3)Simplified calculating method is proposed to work out the frequency response under the effect of dual-frequency excitation.Based on the results of a mass-spring system's response,a conclusion can be drawn that simplified method is a conservative method with small deviation.(4)The vibration response of this rescue ship is figured out with the use of simplified method.And the results indicate that the vibration response of this ship is under the vibration evaluation standard.This thesis introduces the method of direct vibration analysis of a rescue ship.It is of valuable reference to structure arrangement and strength check of analogous ships.