plastic hinges, etc.) assumed in any theory. 



Therefore, in view of these complications, the development of satis- 

 factory design criteria must first be predicated on rigorous mathematical 

 theory with its concomitant idealizations, and then, empirical factors 

 derived from test data can be introduced to "adjust" the theories to take 

 account of those many variables which could not or were not considered. 

 This is the procedure which has found extensive use in many fields for de- 

 veloping empirical design curves, and it is also proving very valuable to 

 the naval architect in the design of pressure hulls. In what follows, con- 

 sideration will first be given to the various theories which form the basis 

 for predicting the elastic and inelastic behavior of ring- stiffened cylin- 

 drical pressure hulls, and then some indication as to how these theories 

 can be used to predict collapse strength. 



Following this there will be a general discussion of the strength-weight 

 potential offered by a variety of ferrous and nonferrous metals, and even 

 some of the new materials such as fiber-reinforced plastics which are 

 being considered for future hull structures of deep-diving vehicles. This 

 final section will also deal with some of the new and untried construction 

 techniques and geometric configurations which are presently receiving 

 detailed investigation. 



17 



