ABSTRACT
Segmental model test is an important and useful method to study the hydrodynamic responses of a ship travelling in waves. It can be used to get the distribution of wave loads in each segmental crosssection. Furthermore, it can also be used to confirm the validity of theoretical results. So this kind of segmental test has an important significance to analysis the wave-induced responses including springing and whipping behavior by a ship model. However, the high cost of segmental model test of a ship will limit the number of test cases. So more and more theoretical calculations will be performed to investigate the wave-induced responses. Gu et al. (2000) had investigated the high-order harmonious component in vertical bending moment of a ship travelling in regular waves. He found nonlinear springing behavior will happen if the frequency of high-order component of the vertical bending moment equals to the eigen frequency of a hull
1 INTRODUCTION
The rapid development of science and technology and the rapid increase of the requirement of bulk carriers in the world make deadweight of bulk carrier being larger and larger. Bulk carriers have already become the main ships forms of bulk cargo transportation both from the existing size and shipping order all over the world. The increasing trend of bulk carriers scale and the widely use of high strength steel to reduce the structural weight results in the hull girder being relative flexible. Springing phenomenon is presented frequently in these bulk carriers when they are travelling in waves. This kind of high frequency vibration will result in the rapid increase of stress cycle number, and then it will result in serious structural fatigue damage of bulk carriers in their travelling courses even in small and moderate sea states. On the other hand, there is another kind of high frequency vibration, whipping, which is caused by slamming events when sea states are being heavy. Whipping will not only have effects on the fatigue damage but also the ultimate strength of ship structure. Thus the safety of ship structure is deeply influenced by springing and whipping, and they will result in the growth of ship maintenance costs.
