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RE: Holes for galvanized bolts

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I work in the petrochemical industry and just about all of our steel is hot
dip galvanized.  Typically all our bolt holes are only the nominal bolt
diameter plus 1/16".  I am not aware of any fabricators or erectors that
have had problems with this.

Christopher M. Cummings, P.E.
Houston, Texas
cmcummings(--nospam--at) <mailto:cmcummings(--nospam--at)> 

		-----Original Message-----
		From:	Bohm, Gabriel [mailto:GBohm(--nospam--at)]
		Sent:	Tuesday, April 13, 1999 4:57 PM
		To:	'seaint(--nospam--at)'
		Subject:	Holes for galvanized bolts

		A certain steel fabricator insists that hole diameters for
		bolts must be the nominal bolt size plus 1/8 inch. They say
it's because
		of the increased bolt diameter due to galvanizing. We would
like them to
		provide standard holes, as the diameter increase is deemed
to be
		negligible, when galvanizing follows the requirements of
		paragraph 4.3.4. 

		We're talking about bearing type connections using ¾, 7/8
and 1 inch
		diameter A325 bolts.

		Neither AISC's Specification for Structural Steel Buildings,
nor RCSC's
		Specification for Structural Joints using ASTM A325 or A490
Bolts appear
		to have the definitive answer to our dispute. Both codes
		standard and oversize holes (bolt diameter, plus 1/16 and
3/16 inch,
		respectively). No word about a 1/8 inch increase. 

		Paragraph J3.2.c of the AISC specification states that
oversized holes
		"shall not be used in bearing-type connections". This leaves
us with the
		standard hole option only. But here's what the RCSC
specification says
		in its Commentary C3 Bolted Parts: "Research has shown that,
		greater latitude is needed in meeting dimensional tolerances
		erection, somewhat larger holes can be permitted for bolts
5/8 inch
		diameter and larger without adversely affecting the
performance of shear
		connections assembled with high-strength bolts. The oversize
and slotted
		hole provisions of this Specification are based upon these

		Well, if bolts in oversize holes perform OK, why does AISC
		their use? In other words, can I accept the fabricator's
		without violating codes? I'm sure some of you have
encountered this
		problem before. Any suggestion will be appreciated.


		Gabe Bohm
		San Dimas, Ca.