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Up Topic Welding Industry / General Welding Discussion / AISC faying surfaces- Class a,b,c
- - By CWI-BRI (*) Date 11-28-2018 15:32
Hey guys,
I have thoroughly searched my 14th edition AISC manual. I read through RCSC 3.2.2 a, b and c. Read through some commentary which lead me to 5.4.1- I see mention of "Appendix A" but cant find it, assuming it maybe a seperate publication. Anyways, long story short- I have some beams that are getting hot dip galvanized on the faying surfaces- What designates the surface as class a, b, or c? I know it needs to be wire brush roughened. Does roughening make it a class c? If unroughened then class a? Is there anything besides the mean slip coefficient involved with the varying classes? (oh and i forgot to mention my specs call out slip critical)
Any guidance/clarification greatly appreciated thank you guys!
Parent - - By 803056 (*****) Date 11-28-2018 15:57
You may need to get a copy of the latest edition of the AISC manual or free download of the RCSC publication.

This is from the RCSC manual:

mean slip coefficient for Class A or B surfaces, as applicable, and
determined as follows, or as established by tests:
(1) For Class A surfaces (unpainted clean mill scale steel surfaces or
surfaces with Class A coatings on blast-cleaned steel or hot-dipped
galvanized and roughened surfaces)
 = 0.30
(2) For Class B surfaces (unpainted blast-cleaned steel surfaces or
surfaces with Class B coatings on blast-cleaned steel)
 = 0.50

Al
Parent - By CWI-BRI (*) Date 11-28-2018 18:24
Thank you Al.

My copy reads the same under 3.2.2 in RCSC- I guess maybe im just overthinking it.

So just to be sure-

If it has clean mill scale and gets coated with class a coating its a class a. also if it is blast cleaned and gets hot dip galv then roughened it's also class a.

then vlast cleaned with class b coating designated it as class b?

So what then designates it as class c?

Do these all have to be determined by test to figure out the slip coeffecient then the class is applied by test results?

Or the most basic answer i need is..... If i have hot dip galv faying surface on a slip critical joint.... what class does it fall under without the galv roughened by wire brush? and what class do i end up with the galv roughened by wire brush?
Parent - - By jwright650 (*****) Date 11-28-2018 18:14
I'm  not sure of your case, and it depends upon what class you need to meet, but in the past we had to let the galvanizer know before they dipped the piece what class you needed to meet. They can skip a step and not quench it. Then there is a paint that goes on the faying surfaces that gives the slip coefficient required to meet the class.
Parent - - By CWI-BRI (*) Date 11-28-2018 18:27
oh ok thank you... ill give you what i know....
The project manager didnt budget to have someone go and wire brush roughen the faying surface after it gets hot dipped. So he is wondering what class we will achieve if we just hot dip it and send it to the customer. Due to the qty of beams getting galvanized, having to roughen all of them will be costly.
Parent - - By CWI-BRI (*) Date 11-28-2018 19:25
i was looking at that exact same website last night but i cant verify anything they say through AISC. Such as "roughening is no longer required". Hard to believe when i cant find that in writing from AISC. Thank you though John.
Parent - By jwright650 (*****) Date 11-28-2018 20:27
The tighter classes require qualification and testing..(like Al already stated) alot more work to cover all of your bases.
Up Topic Welding Industry / General Welding Discussion / AISC faying surfaces- Class a,b,c

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