Values of q ^^^ shown in Table 2. Table 3 shows the calculation 

 of n values for the data from Reference 4.* All the data are shown in 

 Figures 5 through 7. The fitted inelastic buckling curves of Figures 5 

 and 6 were transferred to Figure 8. From this representation of data, 

 a design n curve was selected, which is applicable to both moderately 

 long and long cylinders. The n expression is: 



n = 1.65 - 1.25 (-^ I 0.52 < :ji21. < 1 (10) 



f, I "•— f, 



Gerard developed expressions to predict rj for metallic structures 

 (Ref 11), and these expressions, which can be applied to concrete, are 

 shown graphically in Figure 9. The rj curve from Reference 8 is also 

 shown. Its empirical shape was defined by Limited data where several 

 specimens had low implosion pressures which are not in agreement with 

 that of the new data. The new design n curve has a maximum increase 

 of 35% over that of Reference 8. (For a structure of given geometry, 

 comparative n values are obtained by a linear curve intersecting the 

 origin and the r\ curves . ) 



*The values will be different than those given in Reference 8 because 

 an assumption has been changed. Previously, the 16-inch OD speci- 

 mens with hemisphere end-closures were assumed to be simply sup- 

 ported cylinders. This assumption was made at the time because the 

 analysis of results would be conservative. Data were limited so con- 

 servatism was warranted. In this report, the 16-inch OD specimens, 

 which had an L/D = 4, were assumed to be freely supported or, in 

 other words, long cylinders. 



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