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Double nut, high strength bolts

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I gather this bolted connection is snug tightened only and the connection is fit with a potential for the nut to spin off with vibration, so your fabricator wants to secure the nut with a tack weld.  Would a double nut and lock washer work as well?  It can be installed without the need for a field weld.  The bolts can be installed with two wrenches on the same side of the connection in the field by one person.  The first nut is tightened to spec' and the second one is tightened against the first nut enough to keep them both from spinning.  It only requires a longer bolt and second nut and washer.  The washer can be eliminated if the nuts are flat and practice shows they work for your needs.
I use double bolt connection with slip joints on wood beams that have to move with beam shrinkage or on any connection with thermal or seismic slip.  If the bolt is not wrench-tightened any movement can lead to rolling of the nut or vibration can spin it loose.
Dave Gaines
Pasadena, CA
----- Original Message -----
Sent: Tuesday, June 13, 2006 8:00 AM
Subject: Tack-welding nuts of high strength bolts

Good morning,


A bridge manufacturer has requested tack-welding nuts to a splice plate to make a blind connection of a HSS truss chord splice.  The bolts are ASTM A325, Type 3 (plain) in a snug-tight bearing connection.  Nut specifications are not given.  The splice plate is ASTM A588 steel.


I would appreciate any opinions on tack-welding these nuts.


Thank you.



With respect,


Bob Garner, S.E.


R. Garner

Moffatt & Nichol

Tel.:  (619) 220-6050

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