liquid containers such as storage tanks and elevated tanks, and for much larger 

 structures — powerhouses, penstocks, pressure pipelines, etc. In the case under 

 consideration, there are no restrictions on size and weight if the vessel is built 

 on site; whereas, size and weight considerations become restrictive for a shop- 

 fabricated vessel transported by rail or water to the site. There are other 

 advantages in the prestressed-concrete concept, the most important being that 

 the vessel and building foundations may be integrally designed for more useful 

 load bearing and distribution capacity. The handling equipment for installing 

 and removing a prefabricated vessel (500 tons plus), unless a modular steel con- 

 struction is used, is dispensed with. 



Work on prestressed-concrete design aspects and dynamic action of 

 reinforced concrete structures to shock loads has been underway at NCEL for 

 the past 14 years. With the concentration of talent in this field it appears likely 



that a design could be evolved. 

 This method has been applied by 

 NAVFACasfar backas 1941 

 for a water storage tank, and the 

 first prestressed-concrete barge 

 manufactured in the United States 

 for the Navy is still in service. 



The principle of prestressed- 

 concrete pressure vessels (Figure A-6) 

 is that the hoop stresses are assisted 

 by high-strength steel wires under 

 full load and under no load the 

 tensile stress in steel places the con- 

 crete in compression. Longitudinal 

 tension to retain the end closure 

 is resisted by means of high-strength 



pretensioned 



circumferential 



rods 



pretensioned 



circumferential 



rod 



pretensioned tensile bars or studs going the full 

 height of the vessel and which are 

 anchored in the bottom slab. An 

 inner liner of steel or some resilient 

 material is recommended. 



concrete 



unpressurized pressurized 



Distribution of Hoop Stress 



Figure A-6. Prestressed-concrete concept 



of pressure vessel construction. 



Desirable Features 



1 . Internal pressure vessels of almost 

 any size can be erected in place using 

 this concept. 



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