Fastner Pull Test and Steel Deck KSI

[LimaMike305]

I am a little baffled here. We have a project where we have a 20 guage steel deck, but can't confirm the KSI on the existing deck. No plans,etc. Deck in on top of a mechanical room. The new roofing NOA requires a 22 guage 55KSI steel deck, the fastner test is giving me 530 LBS mean reading. 25 readings - any suggesting on how to determine the KSI of the steel - I can't seem to do the
Stress(psi)=
Cross-Sectional Area (in²)/
Failure Load (lbf)

Any suggestions would be greatly appreciated. See attached file
​

 

[driftLimiter]

I cant believe fastener pullout test is the best way to measure the yield stress of existing metal deck. A lab can take a sample coupon and do a real yield test on it.

Also no file attached.

 

[LimaMike305]

Neither can I - but I have an AOR that thinks I can. LOL

https://files.engineering.com/getfile.aspx?folder=b51e422e-9386-4b8e-b1e5-7bee41f0ef9a&file=Doc5.pdf

That said, the design load is minus 134, the pull test gives us 530 so it exceeds the requirement, but I if anyone knows of how to do the yield stress with a pull test, then maybe the AOR is right

 

[driftLimiter]

If you're just trying to verify a given fasteners strength, then the test with appropriate strength reduction seems fine.

If you need to determine the yield stress of the deck for some other reason than fastener it seems you have a more complicated issue at hand. I myself wouldn't be comfortable backing out the supposed yield stress of the deck based on fastener equations and test data, and then using that yield stress for something else.

 

[LimaMike305]

None other than the NOA calling for 22 guage 55KSI and the AOR asking for the KSI value. Never heard of it being asked for a simple roof install, but who knows. As I always understood it, the fastener test is what determines if the deck can meet the design pressure.

DRIFT THANK YOU MAN. I THOUGHT I WAS GOING CRAZY!!

 

[driftLimiter]

DRIFT THANK YOU MAN. I THOUGHT I WAS GOING CRAZY!!

Just to be clear I never said you weren't going crazy.

 

[LimaMike305]

My man, I have been going at this since 0600 woke up thinking about it. LOL. Anyhow, thank you sir. Much appreciated

 

[SandwichEngine]

If I'm reading your post right, you've performed tests where you pulled on a fastener until it pulled out and you got 530 lbs.

For one, you check pullout using ultimate strength, not yield strength.
For two, it depends on the diameter of the screw.

That being said, assuming a 1/4 (#14) tek screw is your fastener, your results align with an ultimate strength of 80 ksi which is not atypical for deck.

Normally, the safety factor is 2.35 but I've set it to one to try to arrive at the actual pullout value.