The compressive strength, f' was obtained from 3.25x6--inch (83x152- 

 mm) core specimens. The strength of the cores was assumed equal to 

 that of 6xl2-inch (152x305-mm) cast specimens. The smaller size of the 

 core specimens would cause a higher strength relative to 6xl2-tnch 

 cylinders; however, this strength increase would be offset by the effect 

 of drilling which causes a strength decrease. 



With the use of the average wall stress approach as expressed in 

 Equation 3, the material strength factor was calculated as: 



^^im^^P ^ 0.200 



c 2(t/D ) 2(9.5/121) ' 



o 



This factor is shown in Figure 1 for the SEACON hull which had an 



L/D =1.0. 

 o 



The effect of steel reinforcement on the implosion strength of the 

 structure could not be determined from this test. If the reinforcement 

 was considered effective, then the total wall thickness from transformed 

 sections would be 10.07 inches. This represents an increase of 6% over 

 that of the actual wall thickness, which should cause an equivalent 

 increase in the implosion pressure. This single test could not deter- 

 mine such a small percentage difference in strength . 



FINDINGS 



1. The implosion depth for the SEACON structure was 4,700 feet 

 (1430 meters). Core specimens 3.25 inches (83 mm) in diameter by 6 

 inches (152 mm) long taken from the hull gave the uniaxial compressive 

 strength of 10,470 psi (72.2 MPa) . 



2. With the use of the average wall stress equation, the material 

 strength factor, k , was 1.27; the wall stress at implosion was 13,300 

 psi. 



38 



