26GSP,25GSP, and 24GSP Tendons? 1

[Jeoku]

I am doing a load rating on a bridge built built in 1970 with post-tensioned tee section girders. Take a look at the attached as-builts. The tendon types are marked 26GSP, 25GSP, and 24GSP. Does anyone know what these mean? I want to know the strands area and ultimate stress so I can verify the forces shown on the sheet and know what is included in the stress losses.

 

[Ingenuity]

Jeoku,

Looks like grouted button-head system, using 1/4" dia wire, as the table states "shim length" which is a give-away for button-head system.

26 is the number of 1/4" dia wires, with a stated final PT force of 180 kips is about 140 ksi.

Maybe a PRECON or RYERSON - which were licensees for the original BBRV button-heads. When I get home I will check out my old notes and maybe able to post the data.

 

[Ingenuity]

It is a PRESCON system. If you look near the title block of your drawing sheet it is stated "PRESCON Corp" of Colorado - the PT supplier/installer.

Button-head tendons are described by number of wires, type of sheathing, and type of end anchorage/s.

"GSP" nomenclature is:

"G" - GROUTED (alternative is MASTIC for UNbonded tendons)
"S" - STANDARD grooved washer to stressing ends
"P" - spreader PLATE to fixed-end

So in your case all your tendons are grouted, with standard grooved washer stressing ends, with spreader plate at fixed ends.

1/4" dia wire had a GUTS of 240 ksi.

From PCI PT Manual 1 Edition, 1972, Chapter 2:

 

[Jeoku]

I'm impressed that I got such a quick response! Thanks! It looks like I can interpolate between the values easy enough to find 25 and 26 strands. I'll see if I can find this manual online somewhere.

 

[Ingenuity]

Jeoku

Or use A[sub]p[/sub] of the 1/4" dia wire area as 0.049 in[sup]2[/sup] and UTS of 240 ksi and see if that checks out.

 

[hokie66]

Great post, Ingenuity. This is an example of the best use of Eng-Tips. There are thousands of members here, but sometimes you need to find the right one.

 

[Ingenuity]

Thanks hokie.

Good to help out a fellow engineer.

I know I have benefited many, many more times than I have contributed to Eng-Tips, so pleased to give back.

Happy 4th of July, or are 'so Aussie' that you celebrate Jan 26 instead!

 

[hokie66]

I celebrate at every occasion. The 4th comes early here. We will be celebrating a friend's 80th birthday. He is a Kiwi, so not sure what is on the menu, but a few ales and some red will be consumed.