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RE: Galvanized faying surface

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Title: RE: Galvanized faying surface

>As required in RCSC Specification Section 3(b)(5), galvanized surfaces in
>slip-critical connections must be roughened by means of hand wire brushing.
>I have heard one definition of the proper degree of wire brushing required
>as "an amount to visibly alter the surface without disrupting the continuity
>of the galvanizing".

>Can anyone provide a more quantitative description of the degree of wire
>brushing required to satisfy the RCSC specification for the use of
>slip-critical connections?


There is information on the subject in the AISC technical FAQ here:

But as you probably already know, that says about what you quoted already. There is more detailed discussion from a research perspective of the roughening required in the guide to Design Criteria for Bolted and Riveted Joints by Kulak, Fisher and Struik.

The galvanizing tends to solidify with a smooth surface that would get you a slip coefficient on the order of 0.2 without treatment. To get the higher value of 0.35 (recently changed from the 0.4 that was in older RCSC Specification), roughening is required. RCSC gives what I think is a fairly practical and performance-oriented requirement: hand wire brush the surface until it is visibly altered when compared to the untreated galvanizing around the area that's brushed.

Hope this helps.