Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Vibration isolators design of box-frame floating rafts based on impact environment
Jian Qiang Gan a , Jin Pana , Ming Cai Xub,ca Department of Naval Architecture, Ocean and Structural Engineering, School of Naval Architecture, Ocean and Energy Power Engineering,bWuhan University of Technology, Wuhan, Hubei, China;
School of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, Wuhan, Hubei, China
c Wuhan Lituo Bridge Protection Technology CO., LTD, Wuhan, Hubei, China

there is multiple equipment on the ship which need to adopt vibration
isolation treatment, the large floating raft system which forms the wholecabin as a whole can improve the efficiency of vibration isolation andreduce the vibration. The upsizing of floating raft vibration isolation
system has become an inevitable trend.
There are many researches on the design of vibration isolator of floating
raft vibration isolation system. Zhu (1996) proposed the influence ruleof installation deviation of vibration isolator on the overall vibration
isolation effect of double-layer vibration isolation system, which canobviously affect the vibration isolation effect of high frequency band. Du(2005) proposed that the installation position of the upper and lower
isolators is not aligned to reduce the transmission of wide-frequency
vibration to improve the performance of the vibration isolation system.
Wen (2002) and Wang (2000) used the finite element method tonumerically simulate the dynamic characteristics of the floating raftsystem, obtained the anti-impact characteristics of the floating raftsystem through theoretical analysis, and showed that the vibration
isolation system and the hull as a whole had a good anti-impact effect at
high frequency. At present, researches on small floating raft are more
extensive (Sun, 2018; Li, 2019; Sun, 2007). Large floating raft vibration
isolation system has a large number of vibration isolators, large
equipment structure size and weight of hundreds of tons, so its dynamic
characteristics are complex and there are few researches on its impactresponse.
Since the total stiffness of the vibration isolator has an impact on boththe vibration isolation and the impact resistance of the floating raftsystem (Li, 2007). The impact resistance effect in many practicalprojects is not ideal. One of the important reasons is that the installation
position of the vibration isolator is not good enough. Therefore, thestiffness of vibration isolator for floating raft system structure is not thesmaller the better. It is very important to choose the appropriate number
and installation position of vibration isolators and carry out reasonableoptimal configuration. In this paper, through the establishment ofnumerical model of raft plate rack enclosure, frame for main board box
total vibration isolator stiffness of raft and the installation location tostudy the influence law of shock response, put forward three kinds ofsolutions to explore the different stiffness and the effects of theABSTRACT
Floating raft vibration isolation system is an effective method commonlyused for vibration reduction in key cabins of ships, which is developing
towards large-scale. Abaqus, a FEM tool, is employed for the impactanalysis. The FE model of a large box-frame floating raft system hasbeen established. The investigation is conducted in order to determine
the influences of arrangement of vibration isolator for the anti-impact
effect of the floating raft system under vertical impact. In this paper, fivereasonable schemes have been proposed for optimized comparative
analysis. It was shown that a small stiffness can lead to consequencelinearly decreasing the peak acceleration of the floating raft system.
Furthermore, the location of vibration isolator has an influence on thelocal impact resistance as it was shown that more of lower isolators, lessthe stress concentration would be. This study provided relationshiptrends between arrangement of vibration isolator and the anti-impact
effect of the floating raft system, which might be useful in designing
vibration isolator arrangement of large box-frame floating raft system.

KEY WORDS: Large frame box floating raft; Impact analysis; Finite
element method; Vibration isolator.
INTRODUCTION
Ship vibration reduction is very important to improve ship vitality andpersonnel comfort. There are many reasons for ship vibration, such as
the vibration of ship structure caused by various mechanical equipment,
and hull structure vibration caused by sea waves, which is crucial to
improve the ship's vitality and personnel comfort. At present, passive
vibration isolation devices are mainly used for mechanical vibration
isolation of ships, including single-layer vibration isolation devices,
double-layer vibration isolation devices (Li and Xu, 2018) and floating
raft vibration isolation devices (He and Xu, 2013). Floating raft vibration
isolation system has better vibration isolation performance than singlelayer and double-layer vibration isolation systems, so it has become themost commonly used and effective damping method (Wen, 2019). When3257