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Re: double nut anchor bolts

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For typical building base plates there is no requirement (nor necessity) to use double nuts.  I assume you mean two bolts above the base plate as oppose to one nut on top and bottom of the base plate.  Double nutting anchor bolts is normally only required for very tall industrial towers/vessels or industrial equipment with significant vibration (turbines, compressors, etc.).  Torquing the nuts would not be a bad idea but trying to determine a torque value would be nearly impossible with galvanized bolts and concrete which will shrink and creep.  Welding of nuts is very tricky but can be done.  Note that the chemical make up of nuts is different than A36 steel so special welding procedures may be required.

Thomas Hunt, S.E.
ABS Consulting


10/27/2003 01:52 PM

Please respond to

double nut anchor bolts

i have specified a double nut connection on a column base plate at 3/4"
diameter anchor bolt embedded in concrete at a braced frame. grade of steel anchor
bolt is A36, grade of steel base plates are A572 grade 50.  some of the anchor
bolts do project far enough above the base plate to get a double nut.  i have
heard that it is not acceptable to weld nuts to anchor bolts or base plates,
but wouldn't want to weld because all are galvanized.  is it acceptable to
torque anchor bolt instead of using double nut, and what would acceptable torque

thanks in advance

paul franceschi