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

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Thanks.  If I do relent and permit "all thread" I will keep relaxation in 

Prior to the first GLB reinforcing that I did, I spoke with a colleague in 
the prestressing industry about things to watch out for.  His advice was, 
"Use strand chucks to anchor the strands --- don't use wedges."  When the 
supplier of the strand, a very large international prestressing firm, 
requested changing the strand chuck specified to their anchoring system, I 
approved the substitution, thinking, "who knows better the type of anchoring 
to use than the supplier of the strand."  Boy, was I wrong!  Their wedge 
system was difficult to install and time consuming.  On the next job, I stuck 
with strand chucks and the installation and anchoring went along quickly and 
easily.  The contractor easily made up in time saved the additional cost of 
the strand chucks.

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

Gil Brock wrote:

. > Roger,

. > I do not have any figures on relaxation for "all thread". The 
. > manufacturers may not either, in which case you would have to assume it 
. > is like normal reinforcing where, if you are using working stresses 
. > greater than 50 - 60% yield then there would be major problems with 
. > relaxation.

. > Another option would be STRESSBAR (Macalloy or Dywidag) but their 
. > relaxation properties, while defined, are significantly higher than those 
. > for low relaxation strand (about 4% at 70% load according to the 
. > Australian codes).

. > Any of the threaded bar types would have a definite advantage over strand 
. > in anchoring at the ends. A simple plate and nuts is much easier than 
. > wedges etc.

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