Table B-5. Summary of Test Results 





















Coefficient 





C;roup 



t 



(in.) 



t 

 Do 



L 

 Do 



Boundary 

 Condition 



Type of 

 Loading 



t'c 

 (psi) 



I'im 

 (psi) 



''im 

 fj 



of 

 Variation 



(%) 



Remarks 



1 



1.31 



0.024 



2.30 



simple 



short 



7,980 



315 



0.039 



0.7 



- 



2 



1.97 



0.037 



„ 



free 



short 



7,400 



391 



0.053 



13.1 



Specimen 2-4 excluded 



3 



1.97 



0.037 



2.35 



simple 



short 



6,960 



550 



0.079 



5.6 



Specimen 3-4 excluded 



4 



1.97 



0.037 



2.35 



simple 



long 



8,220 



608 



0.075 



9.9 



- 



5 



3.39 



0.063 



~ 



free 



short 



7,990 



1,078 



0,135 



- 



Specimen 5-2 excluded 



Post-implosion views of several specimens are shown in Figures B-8 

 through B-16. For those specimens having a simple-support boundary 

 condition, the failure holes occurred in the midlength region away from 

 the ends (Figures B-8 and B-13). For those specimens having a free- 

 support boundary condition, the failure hole typically occurred at the 

 top end (Figures B-11 through B-15), but the failure hole occurred in 

 the midlength region for specimen 2-1 (the strongest Group 2 specimen) 

 (see Figure B-10). 



The experimental test setup was probably the cause for the failure 

 holes that occurred at the top. When the specimens were fabricated, 

 the top cylinder edge was hand-troweled and therefore uneven. On 

 specimen 5-1 the top end-closure ring was placed on the cylinder with- 

 out the gasket material to observe unevenness. A rather large portion 

 of the mating surface showed a gap of from 1/16 to 1/8 inch (2 to 3 

 mm). A filler material, such as gypsum used in specimens 2-1 and 5-1, 

 filled the gap adequately. However, use of the gypsum was discontin- 

 ued because the material is water soluble, so small leaks grew into 

 major leaks. Epoxy was used as its replacement, but epoxy filler 

 material did not appear to perform adequately. Epoxy has a modulus 

 about one-tenth that of concrete and probably about one-fifth that of 

 gypsum. It wasn't until after specimen 5-2 was tested (at the end of 

 the test program) that it became quite apparent that the epoxy filler 



58 



