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RE: Anchor Bolt Splice

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I believe the answer to your first question is zero, but you should have a
full nut engagement.

Re: a fix for anchor bolts with too little extension but with adequate
embedment, my current project had a similar problem with several 2" anchor
bolts.  The contractor proposed "plug welding" the nuts full.  In all cases
we had at least 3/4" of engagement and most of the columns that had this
condition had 8 anchor bolts with at least 6 having adequate extension.  The
worst was an interior column with 4 anchors bolts with two of them being
short of extension length.  I was skeptical at first, but my structural
engineer assured me with a proper welding procedure, this would be
acceptable.  I didn't' see the procedure or know the particulars, but my
engineer was comfortable with this and it was done.  I doubt there was any
pre-heating done and I assume they used standard E-7018 electrodes.  I'll
try to get more info on this if desired or maybe someone else can provide a
proper welding procedure or something similar.  Or maybe someone else can
tell me this is not the best solution, which I would hate to hear at this
point!

Michael E. Rissell, P.E.

-----Original Message-----
From: Drew Randolph [mailto:drewr(--nospam--at)tetercon.com]
Sent: Monday, January 28, 2002 2:10 PM
To: SEAOC Forum (E-mail)
Subject: Anchor Bolt Splice


Fellow Engineers:
I've got some critical anchor bolts that have been set short in the field.
They are 1 1/4" dia. A449 in tension only.  I'm searching for a fix.  Here
are my questions:

1.  How much thread should be showing above the nut to achieve full design
capacity?
2.  Is there a documented relationship between the number (or length) of
threads actually engaged and the design strength of the bolt/nut interface?
(i.e. a reduction curve when the bolt is shorter than required)
3.  I'm thinking I'll have to weld an extension to the existing bolt.  Is
there a prequalified full pen weld for two equal diameter rods?
4.  Will I need to preheat the base material?
5.  Will I need to specify special electrodes for the operation?

Your help in this matter would be greatly appreciated.  Thank you in
advance.

Andrew Randolph, PE

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