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1958 Prestressing Strand

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pesepeng1

pesepeng1

Structural
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I am investigating an existing precast, prestressed double tee roof constructed in the late 1950's

I'll be x-raying the members to get strand diameters and locations.

Any ideas as to the likely yield strength of the strands?

I'm guessing 270k strands were not available at the time, and if you look at what the post-tensioning industry was doing around about the same time, they were using button head wires rather than multi-wire strands.
 
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Theres some older design guides in the above link that might get you started. But you may end up having to dig through ACI 318-56. I just took a look through my ACI318-51 and it didnt have anything on pre-stress or pre-cast cocnrete construction.
 
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I'd be pretty careful relying on anything of that era because there were a lot of different manufacturers and not enough standards.

That being said.....ASTM A416 was one of the first (if not THE first) to be a standard for strands. It came about in 1957. It's yield strength (at that time) ranges from 212 ksi (Grade 260) to 230 ksi (Grade 270). AISI 5160 and 9260 bars were used in that era as well. The yield strength there is 130 ksi.

[red]EDIT:[/red] Found this at PCI:

 
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Thanks to everyone for their input
 
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And it will be normal relaxation strand, so the relaxation losses will be much higher than we get these days.
 
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From the AASHTO Bridge Evaluation Manual

AASHTO_ur4whx.png


I looked at ACI 318-56; it states the Code isn't to be used for prestressed concrete.
 
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