(c) Location of the worst flat-spot and determination of 

 maximum radial displacement 



(d) The number of buckle lobes at implosion 



Attempts were made to obtain strain data but difficulties were 

 encountered in applying gages to wet concrete. 



Inspection of failed specimens and fragments of concrete from the 

 failure zones yielded data on the deflected shape of the structure and 

 size of the failure hole . 



A detailed presentation of specimen geometry and test results is 

 given in Reference 16. This report summarizes portions of those data. 



SPECIMEN FABRICATION 

 Casting 



The specimens were cast monolithicaUy in steel molds. The same 

 outer mold was used for all specimens, but different inner molds were 

 used to change the wall thickness . The inner molds were built to fold 

 inward so that the diameter became smaller for removal from inside of 

 the concrete cylinder. The inner and outer molds were spaced on the 

 bottom by a ring and on the top by a spreader bar. 



Concrete was placed in the molds by free falling from a dome 

 distribution plate. When the form was vibrated, the concrete flowed to 

 the edges of the dome and fell into the mold. By this technique, the 

 concrete was evenly distributed around the circumference. 



Approximately 20 hours after casting, the mold was removed from 

 the concrete (Figure B-1). All specimens were wrapped in wet burlap 

 and then in polyethylene film . They were subsequently moved to a 

 sheltered storage area where a water drip system kept the burlap wet. 



40 



