3 1/2" X-Strong Pipe wall thickness in AISC 13th

[Splitrings]

Can anyone confirm that a 3 1/2" nominal, x-strong pipe has a wall thickness of 0.318 inches? I have the older 3rd edition of the AISC Steel Manual. I am being told the newest edition, the 13th, has a different wall thickness.

 

[CTW]

Nominal wall thickness is 0.318"
Design wall thickness is 0.296"

The 13th edition added a column for design wall thickness.

 

[neffers]

AISC 13th Edition shows a nominal wall thickness of 0.318" and a Design Wall thickness of 0.296"

neffers

 

[Splitrings]

Thank you both for looking. That 0.022in makes almost a 10% difference in the plastic section modulus. This is why my hand calcs didn't match RISA. Looks like I need to purchase the newest manual.

 

[nutte]

The design wall thickness equals 93% of the nominal wall thickness. They did the same thing to rectangular HSS a few years ago, to reflect what the mills were actually producing.

 

[PMR06]

Related to this... the tables and RISA use the nominal thickness to calculate weight/ft of the sections, but the design thickness for I, S, and A. How the weight can be there without the section properties is beyond me though...

 

[nutte]

It's the same philosphy behind using a detailing k and an engineering k. You use the heavier weight because the shape from the mill could weight that much. You use the lighter section properties because that's the least capacity you could have. Count on a heavier section property, and you may not get it.

 

[PMR06]

nutte, I understand that and agree. My frustration was on a recent project for a contractor in which most of the load was self weight. Literally every pound mattered, and we were stretching the strength of the structure already. The contractor asked what the structure weighed... simple enough question. I explained it could weigh as much as XX (using nominal thickness), but I have to design it as if the sections were their thinnest. He laughed and asked what he would be charged for the steel then.

Anyhow, I just wanted to point out the self weight because it surprised me.

 

[msquared48]

Interesting. I did not know that. I use RISA all the time.

Mike McCann
MMC Engineering

 

[WillisV]

Yes you have to be careful with this - I believe last time I checked SAP2000 uses the reduced properties as well as the reduced weight - so the weights in SAP could be light. I haven't checked in a while though so they might have updated this. I agree with how RISA does it.