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RE: How Can Force in "All Thread" be Det

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Don,

I agree with your caveats and think that your caution to be "a little 
conservative" is probably understated.

In the situation that I have, the material being prestressed is wood with the 
"all thread" connected to steel brackets bolted to the wood.  Take-up of the 
brackets and deformation of the wood, together with taking the sag out of the 
"all thread" would in this case make the calculation of P = delta*A*E/L 
somewhat less than an estimate of the force.

The procedure that I have specified using P/S strands is to apply a 500 lb. 
force (by gauge pressure) to the strands, measure the distance from back of 
bracket to back of bracket, tension, using gauge pressure to determine the 
force in the strand, record the elongation as measured by the jack, measure 
the distance back to back of the brackets again, and try to correlate the 
force and the net elongation of the strand.

I appreciate your contribution to my query.

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

Don Carroll wrote:

. > It may not be the most accurate method but I have used it in the past with
. > good success (although slightly different applications).  Use the old 
. > turn of the nut method, just  PL/AE=elongation.  Your connections would 
. > need to be sufficiently rigid to prevent bending and inaccurate 'turns of 
. > the nut' but it could work if you were a little conservative on the 
. > tension you need.

Don Carroll

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