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RE: Short anchor bolt projection

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Jimmy  C wrote:

>  What would be amiss in field welding the nut to the anchor rod and
welding the 
> nut to the base plate?  

According to responses given in Modern Steel Construction's "Steel
Interchange" (accessible thru www.aisc.org or www.modernsteel.com), plug
welding a less-than-fully-threaded nut to an anchor rod is not recommended.
Charlie Carter points out that there is no test data published regarding
this method, there is no prequalified welding procedure, and it is not clear
what filler metal to use for A563 nut material. Thomas Powell states that a
school in Louisiana had a spectacular failure when such plug welds failed
during high winds. 

I also question the general practice of welding nuts at anchor bolts.
Unfortunately AISC does show nuts welded to anchor bolts in its "Column Base
Plates" Steel Design Guide, where anchor plates are shown tack welded to
nuts at the bottom bearing for anchor bolts. I have been told by a welding
specialist that due to the carbon content of standard nuts, tack welding is
not recommended as it could cause the nut to crack. Full fillet welding
around a nut may be feasible, but proper welding procedures should be used
based on the carbon content. I'd prefer not to rely on the field welder to
follow such procedures, unless clearly defined.