Pien and Lee 



are met, we may anticipate slamming of the cross -deck structure. 



Extension of such an anlysis to irregular seas for monohulls 

 was made by Ochi (1964). If we let 



/oo 

 (|*i R) | / A ) 2 S ("J *«o (20) 



d / v I 30 x o' 



o 



and 



/ 



oo 



(R)_ // L (R) 



2 



v / (w k 30 / A ) s (w ° } dw ° ' (21) 



^o 



we can show that the numbers of probable water contact and slamming 

 of the bottom of the cross structure during n hours are obtained by 



1800 n 



V 



N w =^T— * <- * « (") 



for water contact, and 



N 



s 



1800 n 



(23) 



2 E ( R> 

 = N w e v 



for slamming. 



1.3- Hydrodynamic Loads. 



In this section we will analyze the dynamic loads exerted on 

 ship structure by the oscillatory motions of a ship and the fluid sur- 

 rounding the ship. Other hydrodynamic loads contributed by maneu- 

 vering operations of a ship will not be included. 



Contributing sources for the dynamic loading can be conve- 

 niently separated into two parts. One part is the mass inertial effect 

 due to the acceleration of the ship, and the other is the hydrodyna- 

 mic effect. The hydrodynamic effect is further divided into two parts; 

 one is contributed by the change of pressure distribution caused by 

 incoming and diffracted waves, and the other is contributed by 



478 



