Manufacture of compacted 7-wire high-tensile prestressing strand

[Ingenuity]

I have a project that may require the use of compacted 7-wire prestressing strand. I have experience with 1/2" (12.7mm) and 0.6" (15.2mm) diameter 7-wire prestressing strand, but little with compacted strand.

Does any one know if after regular 7-wire strand is manufactured, does the strand get heated before it goes through compacting dies/rollers, or is is a cold process?

I could not find much manufacturing info on the internet on compacting strand.

TIA

 

[dik]

I'm not aware of it, but it would be interesting to know. I suspect a lot of stand is used for pre-tensioning situations and they may be relying on the slightly improved bond conditions of the non-compact.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Ingenuity]

dik:

Interestingly, it is not used in pre-tensioning applications, and there are no North American manufactures/suppliers either, as far as my research resulted.

I understand that BRIDON in the UK developed it many years ago and it used to be called 'DYFORM', and has occasional use in Europe for some specialty prestress applications. BEKAERT in Belgium manufactures compact strand now - they merged with BRIDON some years back.

Compact wire rope appears common place - so maybe someone knows if the wire rope compaction process is also used to form compact prestressing strand.

 

[dik]

Compact wire rope is common, but I've never seen compact stressing cable. I wasn't aware it was ever manufactured.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Ingenuity]

I may have found my answer from Eurpoean Standard EN10138 Part 3 on prestressing steel:

6.2.4 7-wire compacted strand
Seven wire strand which after stranding has been compacted by drawing or rolling before stress relief
treatment. When stranding and compacting are carried out simultaneously, the straight central wire shall be at
least the same diameter as the outer helical wires. The latter shall have a lay length of 14 to 18 times the
nominal strand diameter.

Since it is compacted after stranding but BEFORE stress relieving, it appears to be a cold drawing/rolling process.

 

[EdStainless]

It is done cold with a low temp stress relief (similar to what they do with springs).
Compacted cable is not flexible and cannot be used where there is any motion.
Other than being slightly smaller I am not sure why someone would use it.

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P.E. Metallurgy, consulting work welcomed

 

[Ingenuity]

Thanks Ed.
My application is motionless.
I am considering the replacement of multiple corroded 1/4" diameter wire tendons in a post-tensioned concrete slab with compacted 7-wire strand, so I need slightly smaller diameter (for installation) AND more tensile strength (section area) to make equivalent capacity.

 

[SwinnyGG]

Other than being slightly smaller I am not sure why someone would use it.

Much less stretch than standard wire rope, which is why I've seen it used. Still pretty rare though.