During the long-term loading test of the structure at 600 feet, 

 results were obtained on the structure's response from initial loading 

 and creep. Although the data are interesting, the pressure load was 

 relatively low, only 14% of its ultimate strength. Of more significance 

 was the implosion test where the structure was lowered into the ocean 

 until failure. Complications occurred during this test which precluded 

 obtaining structural response data, but the implosion pressure was 

 successfully obtained. This test with its results is presented in Appen- 

 dix A. 



Thin-Walled Structures . The thin-waUed cylinder test program 

 encompassed 15 unreinforced concrete specimens, whose dimensions 

 were: 134 inches (3.4 meters) length, 54 inches (1372 mm) OD, and 

 1.31, 1.97, or 3.39 inches (33, 50, or 86 mm, respectively) wall thick- 

 ness. Two different boundary conditions were modeled, a free and a 

 simple support, in order that cylinders of two effective lengths could 

 be studied. The concrete compressive strength ranged between a 

 nominal 7,000 to 8,000 psi (48 to 55 MPa) . 



Structural deformations were monitored by recording radial dis- 

 placements around the circumference of the cylinder. Accurate initial 

 and deflected cross- sectional shapes were obtained which showed the 

 progressive development of out-of-roundness. 



An analytical study using actual material properties and geometric 

 conditions was conducted. A finite-element analysis with an advanced 

 constitutive material model was used. 



This test program on thin-walled cylinders is presented in Appen- 

 dix B. 



DESIGN FOR IMPLOSION 



Thick-Walled Cylinders 



The design approach for unreinforced, thick-waUed cylinders is 

 based on an average stress distribution across the wall of the cylinder 



