2. Several vessels of this concept have been built with diameters in excess of 

 10 feet, and have been found to perform successfully. 



3. Cost of building the vessel in situ is less than the cost of any other vessel 

 concept of similar pressure capability, diameter, and length. 



4. This vessel is safe in operation as the propagation of a fracture crack in the 

 wall is not accompanied by fragmentation. As soon as the overpressure relieves 

 itself through the crack in the concrete, the pretensioned wires and rods in the 

 vessel close the crack. 



Undesirable Features 



1. Internal pressure rating of the vessel depends on the compressive strength 

 of the concrete. Since currently the strength of concrete is less than 10,000 

 psi, the highest internal pressure that such a vessel can contain is also less than 

 10,000 psi. 



2. No design data is available on the incorporation of rapid opening end-closure 

 mechanism into a concrete pressure vessel. 



3. The information on behavior of concrete under cyclic loading in triaxial 

 stress field is at best fragmentary and inadequate. 



4. Inspection of the vessel during service for incipient failure is very difficult. 



Conclusions. The prestressed-concrete pressure vessel concept will 

 permit with reasonable confidence the construction of pressure vessels with 

 pressures less than 5,000 psi and large enough for testing assembled fleet 

 submarines. This pressure vessel concept is at the present time not applicable 

 with currently commercially available Portland cements to the construction 

 of the 10-foot-diameter, 10,000-psi pressure vessel. If cements with compressive 

 strength in excess of 15,000 psi become commercially available prestressed- 

 concrete pressure vessels should be considered for such an application. 



Recommendations. The prestressed-concrete pressure vessel should 

 not be considered for the immediate construction of the 1 0,000-psi, 1 0-foot 

 (internal diameter) pressure vessel. If requirements arise for construction of 

 very large (10 feet < diameter < 100 feet) vessels with less than 5,000-psi 

 pressure requirements, the prestressed-concrete pressure vessel concept should 

 receive first consideration. In the meantime, experimental studies are recom- 

 mended for development of concrete pressure vessel technology to meet such 

 requirements. 



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