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Prestressing rods

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David,

In the late 1950's/early 1960's StressSteel made rods for post-tensioning.  
Since prestressing was in its infancy then, there were very few pretensioning 
beds and post-tensioning was usually the way to go.  I have designed a number 
of bridge deck units (multi-beam units) using the StressSteel information and 
if the rods that you have are StressSteel, I can give you the technical data.

Tanks were usually hooped with steel rods that went thru a clamp that carried 
the ends of the rods tangent to the tank at that point.  These were not 
prestressed and served to function much like barrel hoops.  They were not 
prestressed, but were just subject to hoop tension.  Very close together at 
the bottom, wider apart at the top of the tank.

Tanks that were prestressed were generally prestressed with wires 
continuously wound around the tank.  The Preload Company (still in business) 
was the premier company prestressing tanks in the 1950's.  If there was an 
alternate method, they should have information in their archives.

Hope this helps.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

P.S.  "Square bars," "vintage," --- you are making me out to be an old man!

David L. McCormick wrote:

>>I am evaluating an early 1950s vintage prestressed concrete tank.  The
drawings
I have are incomplete but they indicate either 3/8-inch or 5/8-inch diameter
prestressing rods at spacings varying from 2-3/4 inches to 12 inches.  The
tank
is only 55 feet in diameter and 18 feet tall.

Does anyone have any idea what steel properties would be appropriate to assume
for the rods?  I have been told by a prestressed tank designer/contractor that
square bars used for prestressing in this vintage tank had fu = 140 ksi with
yield stresses in the 60 ksi range.<<

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