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RE: Steel Column Base Plates

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Rick,

This is another issue near and dear to my heart.  Number 1, I prefer a 4
bolt base plate with as wide a spread as possible using headed anchor bolts
(uplift or not).  The ironworker in me prefers shooting in a stack of shims
in the center of the base plate.  The column is placed on the shim stack and
anchor bolts.  For safety I suggest (engineer/iron worker hat on) that the
iron workers drive shims at the perimeter of the plate mid way between
anchor bolts.

I do not like the double nut, because the bolt holes are over sized and to
do it right, you should also use a plate washer between the nut and the base
plate, you need a thicker grout area to accommodate the down nut and allow
for leveling, and any concrete on the threads screws you up when you plumb
the column.  Even if double nuts are provided, my old crew from the early
iron age would not use them.

I prefer a non shrink grout, because I have observed that you get more grout
contact area as opposed to dry packed.

Now if you want to talk about 6 inch thick boiler building column base
plates... that is a different story.  Here I go dreaming of days gone by.

Harold Sprague, P.E.
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: Rick.Drake(--nospam--at)fluordaniel.com [mailto:Rick.Drake(--nospam--at)fluordaniel.com]
Sent: Wednesday, October 14, 1998 12:14 PM
To: seaint(--nospam--at)seaint.org
Subject: Steel Column Base Plates


     During the erection of steel columns, the contractor needs some means 
     of leveling the base plates and plumbing the columns.  Two common 
     choices are 1) steel plates or shims between the foundation and base 
     plate and 2) leveling nuts beneath the base plate.  In both cases 
     grout is placed between the foundation and base plate after the 
     columns are plumbed.  I am interested in current practices for 
     commercial buildings.
     
     What are the advantages and disadvantages of each leveling/plumbing  
     method in high seismic zones?
     
     Do you normally specify a method or leave it up to the preference of 
     the contractor?
     
     Do you normally specify "drypack" grout or nonshrink grout, or do you 
     leave it up to the preference of the contractor?
     
     Thanks,
     
     Rick Drake, SE
     Fluor Daniel, Irvine