Friction Grip Bolts - Suface Preparation for Galvanized Steel

[asixth]

Does anyone call up specific surface preparation for friction grip bolts on their drawings or specifications. I have a galvanized member which I have called up friction grip bolts. I noticed the steelwork shop drawings makes comment that painted surfaces are not allowed around friction grip bolts but doesn't say anything about galvanized steel.

I was reading through an industrial galvanizers association website which says that the galvanized surface should be roughed by grinding or sand-blasting.

Does anyone actually specify this.

http://www.ingal.com.au/FAQ/faq26.html

 

[kelowna]

Yes, that is important.

For painted surfaces, it should be a paint (usually only primer is aplied) that guarantees a minimum friction coeficient. It can be tested quite easily and there are paints that guarantee it.

For weathering steel or unpainted steel, shotblast at factory and protect from contaminants until installation.

For galvanized steel, wire brush to provide a better friction.

 

[connectegr]

I assume you are referring to slip critical connections. Galvanized steel provides a Class C slip coefficient. In 13th Ed, Class C was combined with Class A, since the slip coefficient is nearly the same. Therefore you don't need any additional preparation.

http://www.FerrellEngineering.com

 

[paddingtongreen]

If the nuts and bolts bolts are galvanized and you want friction grip connections, they must be lubricated and torqued by an appropriate method, I preferred turn-of-the-nut for galv'd bolts but if pushed and a good selection are checked in the Skidmore and followed by periodic re-checks, I would allow air wrench to be used.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[azcats]

The section kelowna is referring to is in the RCSC spec section 3.2.2. It notes that only hand wire brushing is allowed.

 

[HgTX]

Power wire brushing will polish the surface and decrease friction. Hence the restriction to hand brushing.

Hg

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