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

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Out of curiosity,  what are you calling a strand chuck?  As in the statement below:

"Use strand chucks to anchor the strands --- don't use wedges."  

Strand chucks are multi-use chucks (with wedges) that are used to anchor pre-tensioning strand against the bulkheads.   They are also used to do things like pull out strand in repairs, to anchor strand for testing, etc.  About the only way to anchor a strand without using wedges is a compression fitting, also referred to as a mechanically attached anchor or a swedge.

You also should probably be clear on what you are specifying and/or the contractor is proposing for bar.  Williams `All-Thread-Bar' is in fact a 150 ksi prestressing bar,  so is the Dywidag `Threadbar'.   

Note also that prestressing bar (ASTM A722) is not low-relaxation,  it is stress-relieved.  The relaxation is much higher than low-relaxation strand.  If the bars are stressed to 0.8fpu,  0.6fpu is tyipcally used as the final effective stress in concrete   I think it would be lower when prestressing wood though.