MOTIONS OF MOORED SHIPS IN SIX DEGREES 



OF FREEDOM 



I -Min Yang 



Tetra Tech, Inc. 

 Pasadena, California U.S.A. 



ABSTRACT 



The equations of motions of a moored ship hav- 

 ing six degrees of freedom were formulated. The 

 mooring force is nonlinear and asymmetrical. A 

 new approach is developed to solve the resulting 

 nonlinear and asymmetrical problem. 



INTRODUCTION 



Recently the development of large ships has attracted many 

 investigators to study motions of moored ships. The introduction of 

 container ships and the increase of oil exploration in deeper water 

 depths make it necessary to have a through understanding of motions 

 of moored structures. For container ships, the operation of loading 

 and unloading containers are controlled by land based huge cranes, 

 extensive ship motion may greatly reduce container loading and un- 

 loading rate. Oil exploration in deep sea needs to drill through the 

 ocean floor from a moored ship (or other moored structures), large 

 motions of the ship may hinder drilling operation. Another related 

 problem is that of a moored buoy system. The effective design and 

 development of such system also require an ability to predict its os- 

 cillatory motions. 



The study of motions of a moored ship is usually limited to the 



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